Access Module - Examples
This page provides a guided introduction to the operation of ACCESS by reference to the retrieval of data for various types of system. Examples of the commands are given in an italic san-serif font. Examples of output are provided. The first three sections cover the essential aspects of ACCESS; Sections 2.4 to 2.7 deal with more specialised features and Section 2.8 with problem handling. The user will not need to have a full knowledge of all these features immediately. On the other hand it will be worth reading about them so that the information can readily be found when needed, especially because decisions made in data retrieval can affect the results of calculations and the ease of obtaining them. For the most part the same considerations apply to the retrieval of data from within MULTIPHASE and the other calculation modules. However, ACCESS gives greater control particularly with regard to changing the priority of data from different databases and dealing with missing data. Any reference to database names does not imply that these will be available to individual users. Users can, in any case, set up mtconfig.txt files to assign aliases to any databases used.
Retrieving and inspection of a simple system from a database
The commands in ACCESS are
- DEFINE
- LIST
- CLASSIFY
- SAVE
- RETURN
The function of these will be described by reference to the system C-H-O.
define system "C,H,O" source demo_a output "cho"!
DEFINE SYSTEM is used to name the components of the system. They are
entered, delimited by commas, as a list in quotes. The data are to be
retrieved from the DEMO_A database.
It is good practice to begin by naming the datafile in which the
retrieved data are to be stored. The data filenames have the extension
.mpi so that in this example the file name will be cho.mpi. The root
name should preferably be short to allow space for the identification by
number of results files from the calculation modules, eg a graph file
produced by MULTIPHASE using cho.mpi as the datafile might be called
ch0127.gph.
The report of this search is obtained using the command LIST.
list system components !
The LIST SYSTEM keywords produce a display, in this case of the components in the system, together with other information. The status of the components cannot be changed within ACCESS.
list system phases substances !
The lists of phases and substances that result from this command would be similar to that given in the table below, except that the status column has already been modified as demonstrated below by the CLASSIFY command. Many substances have also been edited out altogether. In referring to phases when using CLASSIFY it is important to use the numbers or unique abbreviations of the names given in these lists. All condensed substances are assigned to different phases unless their phase labels are identical (see 5.2 and 5.3 of General Introduction to MTDATA). All gases join the same phase. Substances 18 and 19 are gaseous isomers.
The CLASSIFY command allows the status of phases and substances to be changed. Specifically, when multiple databases are being used as in Section 2.3, CLASSIFY is used to revoke the precedence of the first-retrieved data set for a given substance. Substances may be referred to in a number of different ways (see section 4.3 for details). It is however most straightforward to refer to them as SUBSTANCE(s) where 8 refers to a single, group or range of substances expressed by number or by a unique abbreviation of the formula as shown using the LIST command. Phases should be specified using PHASE(p) where p refers to phases in an analogous way.
If all calculations are to be made at high temperatures and moderate pressures, it is useful to delete volatile phases and diamond.
classify absent p(dia,H20,CH40) !
or
classify absent p(2, 4, 5) !
The same effect could have been achieved by using the substances
corresponding to these phases by the command
classify absent s(2, 26,37) !. This method is much less convenient for
solution phases (Section 2.2).
If desirable to save computing time or for other reasons, substances can be deleted from within a phase as follows.
classify absent s(3-10, 12, 14, 16, 18-28, 35, 36, 39, 40, 42) !
Table 2.1 shows selected parts of the listing the phases and substances after this sequence.
(It is possible to omit the "s" for substance eg:
classify absent 3 4 5 6 !. However, in this method the substance
numbers cannot be grouped by means of hyphens, so it is often less
efficient. It is sometimes convenient to begin with a clean slate by
removing all substances and/ or phases and bringing back those of
interest. This is done by entering "*" or "all" to represent all
integers for example:
classify absent s(*) p(*) normal p( 1,3) s( 1, 11,13 etc) ! )
save
The SAVE command has no arguments. When it is entered:
- if the status of a phase is ABSENT, none of the substances in that phase are saved, even when their status is NORMAL;
- equally if all the substances within a phase have an ABSENT status, the phase is not saved, even if its status is NORMAL.
The command SAVE completes the preparation of a datafile having the
extension .mpi. Note that the root name of the output file has to be
defined before the data are saved. If this is not done the data will be
saved to the default file, "def.mpi", which can, however, be renamed
by invoking an operating system command, eg: "$ren def.mpi mf7a.mpi".
Only one SAVE per system definition is effective. In order to prepare a modified datafile for the same system it must be redefined from scratch.
Hint: Up-arrow keys can be used to recover previous commands in some operating systems. Otherwise, the log file generated during the first attempted retrieve can be edited and used as a macro for the purpose of repeating a long sequence of commands
Retrieval of data for substances (edited table of output)
ACCESS OPTION ? list system phases substances !
NUMBER PHASE STATUS MODEL
-------- ---------- -------- ----------------
1 GRAPHITE NORMAL PURE SUBSTANCE
2 DIAMOND absent PURE SUBSTANCE
3 GAS NORMAL IDEAL GAS
4 CH4O absent PURE SUBSTANCE
5 H20 absent PURE SUBSTANCE
NUMBER UNARY/SUBSTANCE STATUS SOURCE
-------- ----------------- -------- ---------
1 C\<GRAPHITE\> NORMAL DEMO\_A
2 C\<DIAMOND\> NORMAL DEMO\_A
5 C3\<g\> absent DEMO\_A
11 CH4\<g\> NORMAL DEMO\_A
13 C2H2\<g\> NORMAL DEMO\_A
15 C2H4\<g\> NORMAL DEMO\_A
17 C2H6\<g\> NORMAL DEMO\_A
18 C3H4\<g\> absent DEMO\_A
19 C3H4\_2\<g\> absent DEMO\_A
26 CH4O\_ absent DEMO\_A
27 CH4O\<g\> absent DEMO\_A
29 CO\<g\> NORMAL DEMO\_A
30 CO2\<g\> NORMAL DEMO\_A
34 H2\<g\> NORMAL DEMO\_A
35 HO\<g\> absent DEMO\_A
37 H2O NORMAL DEMO\_A
38 H2O\<g\> NORMAL DEMO\_A
39 H2O2\<g\> absent DEMO\_A
40 O\<g\> absent DEMO\_A
41 O2\<g\> NORMAL DEMO\_A
42 O3\<g\> absent DEMO\_A
Solution data (elemental components)
With the exception of gases and ideal aqueous solutions, data for solution phases comprise unary data for the end members (and sometimes associates) together with data for binary and sometimes ternary interactions. If a binary interaction is ideal a zero should be explicit in the database. Interactions of order higher than 3 are rare. For crystalline substances, solution is considered to occur by substitution on lattice sites. In many cases there are two or more sublattices, which in general do not have equal numbers of sites. Interstitial sites are treated as forming a separate sublattice, mostly populated by vacancies. This is why the fcc phase has two sublattices in Table 2.2. Sublattices are also used in the ionic liquid model but with variable site ratios.
The interaction or the unary data can be tagged in the database as potentially a source of immiscibility, in which case the status of phases including such data will be listed as "1 M-G". The user can override these settings, as in the following command which cancels a hypothetical miscibility gap in the liquid phase and introduces one for the bcc phase.
class misc(liq) none misc(bcc) 1 !
The name given to a phase is an important item of data and must be consistent; all the data for the phase must bear the same name. The sublattice ratios are included in the phase name so the full name for the fcc phase is exactly FCC_A1:1:1 which, however, can be abbreviated in ACCESS.
The example concerns the system Fe-Cr-Ni, the data for which are assumed to come from a hypothetical database called DEMO_B. If the data are to be used for the calculation of TERNARY phase diagrams (see Section 2.4.9) the order of the components is significant. The output mpi file is named as stl.mpi.
def sys "Fe, Cr, Ni" source none_but demo_b output "stl"!
In this command none_but is used to ensure that previous database
lists are not searched.
Table 2.2 Retrieval of data for the Fe,Cr,Ni system
ACCESS OPTION ? list sys phas subs !
NUMBER PHASE STATUS MODEL
-------- -------------- -------- ----------------
1 LIQUID NORMAL PURE SUBSTANCE
2 SIGMA:8:4:18 NORMAL PURE SUBSTANCE
3 BCC\_A2:1:3 1 M-G PURE SUBSTANCE
4 FCC\_A1:1:1 NORMAL PURE SUBSTANCE
NUMBER UNARY/SUBSTANCE STATUS SOURCE
-------- ------------------- -------- ---------
1 Cr\<LIQUID\> NORMAL DEMO\_B
2 Fe:Cr:Cr\<SIGMA\> NORMAL DEMO\_B
3 Fe:Cr:Fe\<SIGMA\> NORMAL DEMO\_B
4 Fe:Cr:Ni\<SIGMA\> NORMAL DEMO\_B
5 Ni:Cr:Cr\<SIGMA\> NORMAL DEMO\_B
6 Ni:Cr:Fe\<SIGMA\> NORMAL DEMO\_B
7 Ni:Cr:Ni\<SIGMA\> NORMAL DEMO\_B
8 Cr\<BCC\_A2\> NORMAL DEMO\_B
9 Cr\<FCC\_A1\> NORMAL DEMO\_B
10 Fe\<LIQUID\> NORMAL DEMO\_B
11 Fe\<BCC\_A2\> NORMAL DEMO\_B
12 Fe\<FCC\_A1\> NORMAL DEMO\_B
13 Ni\<LIQUID\> NORMAL DEMO\_B
14 Ni\<BCC\_A2\> NORMAL DEMO\_B
15 Ni\<FCC\_A1\> NORMAL DEMO\_B
ACCESS OPTION ? save
SIMPLIFIED MODEL USED FOR PHASE BCC_A2:1:3
SIMPLIFIED MODEL USED FOR PHASE FCC_Al:l:l
Note that the order of search is alphabetic with respect to the elements within each phase but the order of phases depends on the order in which they are found.
Depending on the intended application the list of phases and substances may include redundant phases or substances, for example the gas and liquid. If so they can be classified absent
save
When the data are saved the models are automatically simplified for any sublattice phases for which there is mixing on only one sublattice and a message is output to the screen to that effect.
Searching multiple databases
The number of immediately available databases and their names or aliases corresponds with the entries in the mtconfig.txt file. A list of the available databases can be found by entering a question as follows.
def source ?
In the following example the databases DEMO_A and CVD are chosen.
def out "iphb" sys "In,P,H,Br" source demo_a cvd !
list system phases sub !
By default, substances that are duplicated in different databases will be classified as normal for the first database searched and absent for any subsequent database in the list. For this reason the databases should normally be entered in order of expected value to the problem. If the user had specially prepared the CVD database for a particular problem then it would be appropriate to place it before DEMO_A in the database list.
Once the desired status has been achieved for all phases and substances it is necessary to save the data..
save
Hints: In the use of data from databases of different origins it is
important to avoid saving data for the same substance under different
aliases. For example the same substance might be called Fe203\
On no account should the same name be used for two different phases, as it will result in the two phases being treated as a single solution phase for which interaction data will be required. For this reason names such as "BETA" should be avoided.
It is also desirable to avoid saving data for substances that differ only slightly in their composition but are in fact the same phase. For example Pr~6~O~11~ and PrO~1.333~ would probably be different representations of the same substance.
When switching priority for a substance to a second database it is necessary to make the second occurrence normal after making the first absent.
It is useful to arrange for the list of substances to go to a local printer for purposes of checking and subsequent monitoring of how the results were achieved. Proprietary programs are available for PCs for backscrolling through the screen output and extracting information into files for printing or incorporation into documents.
Systems of non-elemental and charged components
For a number of reasons it is useful to be able to set up datafiles for systems in terms of non- elemental components and these are considered individually below.
Restriction of systems to subsystems
The chemical reactions in a system may be limited in such a way that the effective number of components is less than the number of elements. For example, the reaction of ammonia with hydrogen chloride at low temperatures does not produce nitrogen, hydrogen or chlorine at a significant rate, so "NH3,HCl" is a better description of the system than "N,H,Cl" for these conditions.
ACCESS operates by retrieving the names of all substances including solution species corresponding to the elemental system and then eliminating those that are not within the possibly more restricted system defined by the non-elemental components. This provides the user with the opportunity to see the names of the eliminated substances and to make a judgement about the validity of the current choice of components. The substances that cannot be formed from a linear combination of the defined components are given the "EX-SYSTEM" status. This status must not be changed if errors are to be avoided.
The use of dummy elements to represent metastable molecules is considered in Section 2.4.8.
Choosing components to match experiment
Even though a choice of components other than the elements normally has no effect on the operation of MULTIPHASE and other calculation modules, there are circumstances under which it may be beneficial. The objective in seeking the best choice of components should be to imitate experiment as far as possible, defining the system in terms of independent rather than dependent variables. As a simple example, water (gaseous or liquid) is the dominant product of the H-O system. At low temperatures especially, the amount of molecular hydrogen and oxygen coexisting with water in a mixture of exact composition HZO is immeasurably small, possibly less than one molecule in one mole of water, and an exact mass balance at these low levels cannot be attained. Problems in calculating equilibria in such systems can in most cases be overcome by defining the system as "H20,0" or "H20,H" rather than as "H,O". If the system is defined as "H20,H", negative amounts of H imply an excess of O over that required to make H~2~O.
Choosing components for convenience in stepping
For convenience in stepping compositions along a particular direction in the system it may be useful to choose one of the components to correspond with this direction. For example if it were desired to calculate the effect of adding methane to a system, the component list could include CH4 and H rather than C and H. (MULTIPHASE does offer another method of achieving a similar result, namely the setting of named start and finish compositions.)
Reference states and component Selection
In MULTIPHASE it can be useful to represent a component such as oxygen (for which the monatomic form is not the reference state) as the dimer, 02, when the data are retrieved. If this is done and the gas is made the reference phase for oxygen in MULTIPHASE, then calculated thermodynamic functions will have values that are in line with standard tabulations.
Electronic charge as a component
Although it is possible for calculations to be made in systems open to electronic charge, particularly commonly in COPLOT, this is rarely useful in MULTIPHASE. The amount of charge in a closed system and indeed any phase within the system must be zero, and therefore the electron is not formally a component of the system overall. Nevertheless, either the electron or another charged species must be declared in the list of components to allow the formation of ionic species to be quantified. The same applies when charged species are used to model the thermodynamic properties of other types of phase, notably ionic solids and melts. If the charged component is made the last in the system list, ACCESS organises it as a constraint on the system that fixes the amount of charge in the system and in each phase to be zero, as in the following example.
def sys "CaO,FeO,Fe203,A/203,Si02,0/-2" source oxdemo !
The inclusion of both FeO and Fe203 in the system definition effectively makes oxygen a component. As a result data will be retrieved not only for unaries (charged or uncharged) that lie within the space limited by the components but also for any of the metallic elements and oxygen itself.
If it is desired to make a charged species an explicit component in the calculation modules (ie one for which the amount can be set), it should be included early in the component list. Two charged components should not be included in the same system definition. ACCESS permits charge to be an explicit component only for systems including aqueous or gaseous phases. The following examples show the definition of an iron-water system in different ways. In each case four components are defined and an identical set of species retrieved from the databases. However, in the first two of the examples at least one charged species is included early (ie not last) in the list. Only in these two cases will the components in the resultant datafile be such as to allow the amount of charge to be fixed or free to vary from zero in the calculation modules. Whereas, in the third and fourth examples, it will not be possible to specify the amount of charge, since this is constrained to zero.
def sys "Fe,H/+,H2,H20" source aqex hot !
def sys "Fe,/-, 02, H20" !
def sys "Fe,H,O,/-"!
def sys "Fe304, H20, H2,H/+" !
list sys sub !
Aqueous systems
clas absent p(H20) ! save
If the aqueous phase is present, water with the phase label H20 must be made absent, leaving data for H2O. The AQEXTRAS database includes data for the conventional (ie not real) aqueous electron. Unless calculations are to be made using COPLOT it is preferable to classify /- as absent in ACCESS before saving the data to a datafile.
If calculations require a charged species to be an explicit component in an aqueous phase, it is essential that all charged gaseous species are made absent. The reason for this is that MTDATA currently has no knowledge of electric potential. Hence, if charge is an explicit component it would be redistributed between aqueous and gaseous phases unless the above precaution were taken.
Isotopes
The data retrieval system and calculation modules in principle allow isotopes to be considered. The main current limitation is that none appears in the look-up table of atomic weights that is incorporated into MTDATA and therefore no calculations can be made involving mass fractions. Moreover, no data are provided for isotopic species in the SGTE databases. Hence users wishing to work with isotopes will have to provide their own data. It should be noted that incorporating data for all but rare isotopes will upset the data for more abundant species. Perhaps the worst case is that of lithium for which the thermodynamic properties of 6Li and 7Li are significantly different and the abundances are comparable. In such a case it would be desirable to introduce data for two or more distinct new elements, for example Lj and Lk, and to omit the data for Li. The reader should note that the provision of thermodynamic data for individual isotopic species is not as straightforward as it might seem, as it is necessary to decouple the data for the individual isotopes from the previously assessed data for the mixture.
Dummy elements representing molecules
There are many examples in chemistry in which molecular groups are stable in practice though not at true equilibrium. For example, during the formation of complexes in aqueous systems a complexing agent such as ethylenediamine cannot be in full equilibrium with the system. For such a case it would be possible to generate data for a minimal neutral form of the complexing agent, assigning it a two letter symbol as though it were an element. Data could then be introduced into a database for the complexing agent and its compounds with the elements or ions. ACCESS would allow the retrieval of these data in the normal way but, as at present with isotopes, it would not be possible to undertake calculations involving mass.
Using this method of providing molecules with aliases it is possible and entirely justifiable for a system to contain more components than elements.
Choosing a component order for TERNARY
The TERNARY module allows the arrangement of the components around the triangular phase diagram to be changed. However, the need for the change can be avoided by appropriate selection of the order when defining the components of the system. In TERNARY the default sequence puts the first component at bottom left and orders the other components clockwise.
define system "CaCI2,KCI,ZnC/2" source saltsO output "s37a"!
In this case the model used has taken no account of charge, whereas it is normal to employ a model that recognises the existence of charged entities in the liquid and solid solutions. The particular system discussed below, namely NaCl-NaI-KCl-KI, appears to have four components. However, these are linearly related by the chemical equation:
NaCl + KI = NaI + KCl
which reduces the number of components necessary to define the overall system to three. The system is said to be reciprocal. Charge is used to model the properties of one of the phases and this requires the addition of one of the ionic species to the list of components raising the total once more to four. Note that it would be incorrect to replace C1/- by /-, since no combination of the components would then generate the charged ions. The charged component must be the last in the list so that it is not treated as a formal component but as a constraint on the system.
define system "NaCI,KCI,NaI,CI/-" source salts1 !
On reciprocal plots the first pair of components (taken in the sequence 1,2,3,1) having a common first element will be assigned to the top left and top right of the diagram. In the above example, because the third and first components both contain Na as the first element, they will occupy respectively the upper left and upper right corners of the diagram.
Hints for dealing with large systems
By default the maximum number of components that can be handled by MTDATA is 30. For systems involving several elements that form many compounds together, there is a possibility that a search of multiple databases will retrieve more than the upper limit of substances for the ACCESS module. This is more likely for versions that have been deliberately configured for small systems.
In such a case, if a search of the individual databases reveals that most of the data can be found in one of the databases eg SGTE but a few substances must be retrieved from other databases, it is possible that a very large overlap will cause the maximum number of species to be exceeded. If so the following procedure can be followed. Use the UTILITY module to create a temporary database and include it in your database list in the mtconfigtxt file. Save the additional data into the temporary file by means of the THERMOTAB module. Once this is done go back to ACCESS and do a search of SGTE and the temporary database only.
If necessary, MTDATA can be reconfigured for more substances or indeed for less.
Model simplification
When mixing occurs only on one of the sublattices of a phase with more
than one sublattice and this sublattice has a site ratio of unity, the
default option is to simplify the data as though there was no sublattice
structure. This speeds up calculations. However, if desired the full
model can be retained by changing an MTDATA configuration variable,
either interactively or in the mtsignon.txt file, by entry of
[SUBLATTICE=NOCHANGE. By entry of [SUBLATTICE=SIMPLIFY the default
can be restored.
Implicit component
At the request of a user an MTDATA configuration variable has been added to allow a named component to be added automatically to all systems defined whilst the variable is given a value other than NONE. For example the entry [IMPLICIT_COMPONENT=O/-2, either interactively or in the active mtsignon.txt file would add "O/-2" at the end of any defined system name. It is recommended that an implicit component is declared only in an mtsignon.txt file in a work area used exclusively in connection with appropriate systems.
Problems caused by missing data
The way the ACCESS module works when data are missing can be modified by
the user's setting of an MTDATA configuration variable MISSING_DATA.
This has the default setting of FAIL, which can be changed, either
semi-permanently in the mtsignon.txt file or, temporarily at the ACCESS
prompt, by entry of [MISSING_DATA=CONTINUE. The value can be restored
to FAIL in the same manner.
The example given in Tables 2.8.1 to 2.8.6 was obtained using the system Fe-Cr-Ni-C, which is of major importance in steels. The action required by the user would depend very much on the application. For example data for the liquid would not be needed unless the steel were to be melted. The general principles will be considered before the details of the example. In the following description any reference to MULTIPHASE should be taken to imply any of the equivalent calculation modules within MTDATA.
Binary interactions
If datasets for two unaries are found for a given phase, ACCESS expects
to find data relating to their interaction in solution in that phase. If
no interaction data are present when the command save is entered, what
happens depends on the status of MISSING_DATA. If MISSING_DATA=FAIL,
data equivalent to ideal interaction (excess Gibbs energy = 0) will be
inserted in the saved mpi file but the data will be preceded by an error
flag (a line containing the word "REMOVE") that will cause the reading
of the mpi file by the calculation modules to be aborted and an error
message sent to the screen. The error flag will be omitted if
MISSING_DATA=CONTINUE and the .mpi file will load into MULTIPHASE with
the problem phases classified as absent.
In either case a warning message is given that a file misbin.dbl has been generated containing zero interaction data sets for the solutions lacking interaction data. These data can be compiled using the UTILITY module into a separate database or, if the original database were "owned" by the user, the misbin.db1 file could be appended to the data loading file (extension name .loa or .dbl) and the whole recompiled. The retrieval of the data could then be repeated. See the hint at the end of Section 2.1.
An alternative but strongly deprecated method is to use a text editor (not a word processor) to search for and delete the lines containing "REMOVE" that prevent the .mpi file being used.
In the nature of things the phases for which data are missing are likely to be the less common phases. In the example of Table 2.8.3 many datasets for binary interactions are indicated as missing. These datasets will not be needed for systems if elements that stabilise the phase are absent. For such systems the best procedure may be to classify the phase as absent. This is a significant step which should be a conscious decision of the MTDATA user. It is for this reason that the option of manually omitting the phase or automatically including ideal data have been made user choices rather than the default. The setting of the MISSING_DATA variable forms part of the user's options.
Unary data
Unary data may also be missing, more probably for sublattice than simple phases. If unaries are missing, error messages will be sent to the screen when the data are saved, listing which datasets are missing. The best procedure to adopt is first to check whether the phase or phases in question may be unstable. If the phase is not needed, the retrieval process should be repeated as before but the phase should be classified as absent before the save command is issued. It is possible that ACCESS has inferred the need for the missing unary from the presence of another in a sublattice phase. In such cases omission of that unary may allow the save to proceed smoothly.
If the phase is considered unlikely to form or the component is considered unlikely to dissolve in the phase but there is a degree of uncertainty, the simplest option is to set the MISSING_DATA configuration variable to CONTINUE. When the data are saved a value of zero will be assigned to the unary and the status of the phase will be absent when the data are read by MULTIPHASE.
If on the other hand the phase is potentially important to the system and the component likely to dissolve in it, the user should create or add to his own data loading file and insert data for the missing unaries using a text editor. The format for such data should be as specified in the UTILITY handbook or as output by THERMOTAB when data are listed. The misbin.dbl file created during the save operation will provide an excellent foundation for adding "real" data. The UTILITY module should then be used to compile the load file into a database (eg mydata.dbs/inx) and to include this database in the current list specified in the mtconfigtxt file. The data retrieval process using ACCESS can then be repeated with the mydata database specified before other databases. See the hints given in relation to missing binary data. The UTILITY manual should be consulted on the procedure for database creation.
Magnetic data
ACCESS decides whether a phase requires magnetic data on the basis of the existence or absence of magnetic data for the first unary retrieved for the phase. If no magnetic data flag is present for that unary, ACCESS will omit any magnetic data found for the other unaries and warnings to this effect will be given.
If magnetic data are present for other unaries the user should create or add to his own data loading file the existing data for the first unary with explicit magnetic data appended even if the values are zero. The THERMOTAB module can be used to generate a file containing the existing data which can be edited to include magnetic data, normally an explicit zero. This file can then be used as a data loading file or it can be appended to an existing data loading file. The procedure described above for handling missing unary data can then be followed.
Mixed models
For the present at least ACCESS will not save files containing data for phases containing substances represented by more than one temperature expression, eg G-Hser and Cp formats. If for example one retrieves data for a system from UNARY (G-Hser format) and SGSUB (Cp format), any data for gaseous species from UNARY must be classified as absent and the data for the same species in the SGSUB classified normal before the data are saved (This will not apply if you are using the G-Hser version of the SGSUB database). Care should also be taken not to mix incompatible data for the unaries and interactions in solution phases.
Reference states must also be consistent. The data for unaries in the SGTE databases are referred to the elements at 298.15 K. They should not be mixed with what are known as lattice stability data, for which the reference is an arbitrary phase at current temperature.
Example for the Fe-Cr-Ni-C system
Table 2.8.1 shows a list of the phases for which at least some datasets were present in sgsol version 3.01. At this stage an entry of NORMAL in the STATUS column does not guarantee that the data for the phase are complete. Moreover, the entries in the MODEL column do not fully distinguish different types of substance. The MODEL column is updated after the data are saved. The phase type is given more completely in Table 2.8.4 which shows the status of data retrieved by MULTIPHASE after incomplete datasets were saved.
The list of unaries is given in Table 2.8.2. A metallurgist looking at the list of phases in Table 2.8.1 would notice immediately a number of unexpected phases and others that were rather unlikely to form. Some of these phases could certainly be classified as absent at this stage. However, for illustrative purposes, all the data in the example are saved so that the diagnostics can be explained. Note that MISSING_DATA has been set to CONTINUE.
Data retrieval for the Fe,Cr,Ni,C system (list of phases)
ACCESS OPTION ? [MISSING_DATA=CONTINUE
ACCESS OPTION ? define sys "Fe,Cr,Ni,C" source 5950! out "st1b"!
SEARCHING EOR SYSTEM Fe,Cr,Ni,C
sgsol - SGTE Solution Database 3.01 - 19/7/93
ACCESS OPTION ? list system phases!
NUMBER PHASE STATUS MODEL
-------- ------------------- -------- ----------------
1 DIAMOND_A4 NORMAL PURE SUBSTANCE
2 GRAPHITE NORMAL PURE SUBSTANCE
3 LIQUID NORMAL PURE SUBSTANCE
4 GAS NORMAL IDEAL GAS
5 BCC_A2:1:3 NORMAL PURE SUBSTANCE
6 CEMENTITE:3:1 NORMAL PURE SUBSTANCE
7 FCC_A1:1:1 NORMAL PURE SUBSTANCE
8 HCP_A3:1:.5 NORMAL PURE SUBSTANCE
9 KSI_CARBIDE:3:1 NORMAL PURE SUBSTANCE
10 M3C2:3:2 NORMAL PURE SUBSTANCE
11 M7C3:7:3 NORMAL PURE SUBSTANCE
12 M23C6:20:3:6 NORMAL PURE SUBSTANCE
13 CBCC_Al2:1:1 NORMAL PURE SUBSTANCE
14 CUB_Al2:1:1 NORMAL PURE SUBSTANCE
15 FE4N:4:1 NORMAL PURE SUBSTANCE
16 FECN_CHI:2.2:1 NORMAL PURE SUBSTANCE
17 M5C2:5:2 NORMAL PURE SUBSTANCE
18 V3C2:3:2 NORMAL PURE SUBSTANCE
19 CR3SI:3:1 NORMAL PURE SUBSTANCE
20 CRSI2:1:2 NORMAL PURE SUBSTANCE
21 CHI_Al2:24:10:24 NORMAL PURE SUBSTANCE
22 SIGMA:8:4:18 NORMAL PURE SUBSTANCE
23 AL5FE4 NORMAL PURE SUBSTANCE
24 AL3NI2:.6:.4 NORMAL PURE SUBSTANCE
25 ALNI_B2:.5:.5 NORMAL PURE SUBSTANCE
The diagnostic messages are given in Table 2.8.3. At first the list looks rather daunting but in fact only a few factors are causing all the messages. Problems not revealed by the diagnostics (eg for the M3C2 and M7C3 phases) are potentially equally important and will be considered later. The first seven lines merely show that a sublattice model for a phase has been simplified because there was solution on at most one of the sublattices. The important information summarised at the foot of the table refers to five phases. Of these the HCP phase occurs in alloys based on other elements eg Ti and for modelling specific carbide phases. For this system the phase can be ignored. The CBCC_A12 and CUB_A13 phases are found in manganese rich alloys. These phases can therefore safely be removed from the system. The two remaining problems concern CEMENTITE and M23C6 which need further consideration.
List of substances retrieved for the Fe,Cr,Ni,C system
ACCESS OPTION ? list system subs !
NUMBER UNARY/SUBSTANCE STATUS SOURCE
-------- --------------------- -------- --------
1 C\<DIAMOND A4\> NORMAL SGSOL
2 C\<GRAPHITE\> NORMAL SGSOL
3 C\<LIQUID\> NORMAL SGSOL
4 C\<g\> NORMAL SGSOL
5 C2\<g\> NORMAL SGSOL
6 C3\<g\> NORMAL SGSOL
7 C4\<g\> NORMAL SGSOL
8 C5\<g\> NORMAL SGSOL
9 C6\<g\> NORMAL SGSOL
10 C7\<g\> NORMAL SGSOL
11 Cr:C\<BCC A2\> NORMAL SGSOL
12 Cr:C\<CEMENTITE\> NORMAL SGSOL
13 Cr:C\<FCC A1\> NORMAL SGSOL
14 Cr:C\<HCP:A3\> NORMAL SGSOL
15 Cr:C\<KSI CARBIDE\> NORMAL SGSOL
16 Cr:C\<M3C\> NORMAL SGSOL
17 Cr:C\<M7C3\> NORMAL SGSOL
18 Cr:Cr:C\<M23C6\> NORMAL SGSOL
19 Fe:Cr:C\<M23C6\> NORMAL SGSOL
20 Cr:Fe:C\<M23C6\> NORMAL SGSOL
21 Fe:C\<BCC A2\> NORMAL SGSOL
22 Fe:C\<CBCC A12\> NORMAL SGSOL
23 Fe:C\<CEMENTITE\> NORMAL SGSOL
24 Fe:C\<CUB A13\> NORMAL SGSOL
25 Fe:C\<FCC A1\> NORMAL SGSOL
26 Fe:C\<FE4N\> NORMAL SGSOL
27 Fe:C\<FECN7CHI\> NORMAL SGSOL
28 Fe:C\<HCP A3\> NORMAL SGSOL
29 Fe:C\<KSI CARBIDE\> NORMAL SGSOL
30 Fe:C\<MSC\> NORMAL SGSOL
31 Fe:C\<M7C3\> NORMAL SGSOL
32 Fe:C\<V3C2\> NORMAL SGSOL
33 Fe:Fe:C\<M23C6\> NORMAL SGSOL
34 Ni:C\<BCC A2\> NORMAL SGSOL
35 Ni:C\<CEMENTITE\> NORMAL SGSOL
36 Ni:C\<FCC A1\> NORMAL SGSOL
37 Ni:C\<HCP A3\> NORMAL SGSOL
38 Ni:Ni:C\<M23C6\> NORMAL SGSOL
39 Cr\<LIQUID\> NORMAL SGSOL
40 Cr\<g\> NORMAL SGSOL
41 Cr:Cr\<CR3SI\> NORMAL SGSOL
42 Cr:Cr\<CRSI2\> NORMAL SGSOL
43 Cr:Cr:Cr\<CHIiA12\> NORMAL SGSOL
44 Fe:Cr:Fe\<CHI A12\> NORMAL SGSOL
45 Fe:Cr:Fe\<SIGMA\> NORMAL SGSOL
46 Fe:Cr:Cr\<CHI A12\> NORMAL SGSOL
47 Fe:Cr:Cr\<SIGMA\> NORMAL SGSOL
48 Cr:Cr:Fe\<CHI A12\> NORMAL SGSOL
49 Ni:Cr:Fe\<SIGMA\> NORMAL SGSOL
50 Fe:Cr:Ni\<SIGMA\> NORMAL SGSOL
51 Ni:Cr:Ni\<SIGMA\> NORMAL SGSOL
52 Ni:Cr:Cr\<SIGMA\> NORMAL SGSOL
53 Cr:Va\<BCC A2\> NORMAL SGSOL
54 Cr:Va\<CBCC A12\> NORMAL SGSOL
55 Cr:Va\<CUB7A13\> NORMAL SGSOL
56 Cr:Va\<FCC Al\> NORMAL SGSOL
57 Cr:Va\<HCP A3\> NORMAL SGSOL
58 Fe\<AL5FE4\> NORMAL SGSOL
59 Fe\<LIQUID\> NORMAL SGSOL
60 Fe\<g\> NORMAL SGSOL
61 Fe:Va\<BCC\_A2\> NORMAL SGSOL
62 Fe:Va\<CBCC\_A12\> NORMAL SGSOL
63 Fe:Va\<CUB\_A13\> NORMAL SGSOL
64 Fe:Va\<FCC\_Al\> NORMAL SGSOL
65 Fe:Va\<HCP\_A3\> NORMAL SGSOL
66 Ni\<LIQUID\> NORMAL SGSOL
67 Ni:Ni\<AL3N12\> NORMAL SGSOL
68 Ni:Ni\<ALNI\_B2\> NORMAL SGSOL
69 Va:Ni\<ALNI\_B2\> NORMAL SGSOL
70 Ni:Va\<BCC\_K2\> NORMAL SGSOL
71 Ni:Va\<CBCC\_A12\> NORMAL SGSOL
72 Ni:Va\<CUB\_A13\> NORMAL SGSOL
73 Ni:Va\<FCC\_A1\> NORMAL SGSOL
74 Ni:Va\<HCP\_A3\> NORMAL SGSOL
NORMAL SUBSTANCE COUNT = 74
Table 2.8.3 Messages sent to screen after saving the data without reclassification
ACCESS OPTION ? save
SIMPLIFIED MODEL USED FOR PHASE M3C2:3:2
SIMPLIFIED MODEL USED FOR PHASE FE4N:4:1
SIMPLIFIED MODEL USED FOR PHASE FECN_CHI:2.2:1
SIMPLIFIED MODEL USED FOR PHASE M5C2:5:2
SIMPLIFIED MODEL USED FOR PHASE V3C2:3:2
SIMPLIFIED MODEL USED FOR PHASE CR3SI:3:1
SIMPLIFIED MODEL USED FOR PHASE CRSI2:1:2
SIMPLIFIED MODEL USED FOR PHASE AL3NI2:.6:.4
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:C<CEMENTITE:3:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:C<HCP_A3:1:.5&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:Va<HCP_A3:1:.5&>
ERROR: NO DATA FOUND FOR UNARY Cr:Ni:C<M23C6&>
ERROR: NO DATA FOUND FOR UNARY Fe:Ni:C<M23C6&>
ERROR: NO DATA FOUND FOR UNARY Ni:Cr:C<M23C6&>
ERROR: NO DATA FOUND FOR UNARY Ni:Fe:C<M23C6&>
ERROR: NO DATA FOR BINARY INTERACTION Cr:Cr,Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:Cr:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Cr:Fe,Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:Fe:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Fe:Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Fe:Cr,Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Fe,Ni:Cr:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Fe:Fe,Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Fe,Ni:Fe:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Fe,Ni:Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Ni:Cr,Fe:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Ni:Cr,Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOR BINARY INTERACTION Ni:Fe,Ni:C<M23C6:20:3:6&>
ERROR: NO DATA FOUND FOR UNARY Cr:C<CBCC_A12&>
ERROR: NO DATA FOUND FOR UNARY Ni:C<CBCC_A12&>
ERROR: NO DATA FOR BINARY INTERACTION Cr:C,Va<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Fe:C<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:C<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Fe:Va<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:Va<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Fe,Ni:C<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Fe,Ni:Va<CBCC_A12:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Ni:C,Va<CBCC_A12:1:1&>
ERROR: NO DATA FOUND FOR UNARY Cr:C<CUB_A13&>
ERROR: NO DATA FOUND FOR UNARY Ni:C<CUB_A13&>
ERROR: NO DATA FOR BINARY INTERACTION Cr:C,Va<CUB_A13:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Fe:C<CUB_A13:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:C<CUB_A13:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Fe:Va<CUB_A13:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Fe,Ni:C<CUB_A13:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Cr,Fe:C<CUB_A13:1:1&>
ERROR: NO DATA FOR BINARY INTERACTION Ni:C,Va<CUB_A13:1:1&>
****** 5 PHASES IDENTIFIED WITH INCORRECT OR MISSING DATA ******
PHASE: CEMENTITE:3:1
ERROR: Missing data for binary interaction(s)
PHASE: HCP_A3:1:.5
ERROR: Missing data for binary interaction(s)
PHASE: M23C6:20:3:6
ERROR: Missing data for unary(s)
PHASE: CBCC_A12:1:1
ERROR: Missing data for unary(s)
PHASE: CUB_A13:1:1
ERROR: Missing data for unary(s)
****** GOOD DATAFILE CREATED (but missing/inconsistent data) ******
****************************************************
* FOR MISSING INTERACTION DATA SEE FILE misbin.dbl *
****************************************************
CEMENTITE, M3C, is unlikely to form in steels that are rich in Cr because the M23C6, M7C3 and M3C2 phases will form in preference. However, CEMENTITE is more likely to form in high carbon alloys that are poor in Cr and other elements that are strong carbide formers. The problem with the data lies with the missing dataset for the binary interaction between Cr and Ni on the first sublattice. This is written Cr,Ni:C. The best course for the moment is to allow data for the phase to be saved with a zero for the excess Gibbs energy for this interaction. If the phase is reclassified as NORMAL after the data are recovered by MULTIPHASE and it is found that both Cr and Ni are concentrated in the phase, then critically assessed data should be sought to replace the zero. In fact the data are readily available and should be in the next version of SGSOL. They are already included in SGSPLUS which is available from your MTDATA support centre.
Table 2.8.4 Recovery by MULTIPHASE of the data saved in table 2.8.2
ACCESS OPTION ? ret multiphase
MULTIPHASE OPTION ? define data "st1a"!
Date and time of run 5-JAN-94 14:47:49
* DATAFILE : st1a.mpi - CREATED 14:46 05/01/94
* SYSTEM : Fe, Cr, Ni, C,
* NUMBER OE PHASES : 25
* NUMBER OE SPECIES : 80
*
********************************
* UNASSESSED OR INCORRECT DATA *
********************************
*************************************
* WARNING/ERRORS HAVE BEEN DETECTED *
*************************************
2 Error(s): UNASSESSED DATA - Missing data for binary(s)
3 Error(s): UNASSESSED DATA - Missing data for unary(s)
MULTIPHASE OPTION ? list sys phas!
NUMBER PHASE STATUS MODEL
-------- -------------- -------- ----------------
1 DIAMOND A4 NORMAL PURE SUBSTANCE
2 GRAPHITE NORMAL PURE SUBSTANCE
3 LIQUID NORMAL REDLICH-KISTER
4 GAS NORMAL IDEAL GAS
5 BCC_A2 NORMAL SUBLATTICE
6 CEMENTITE absent SUBLATTICE
7 FCC_A1 NORMAL SUBLATTICE
8 HCP_A3 absent SUBLATTICE
9 KSI_CARBIDE NORMAL SUBLATTICE
10 M3C2 NORMAL PURE SUBSTANCE
11 M7C3 NORMAL SUBLATTICE
12 M23C6 absent SUBLATTICE
13 CBCC_A12 absent SUBLATTICE
14 CUB_A12 absent SUBLATTICE
15 FE4N NORMAL PURE SUBSTANCE
16 FECN_CHI NORMAL PURE SUBSTANCE
17 M5C2 NORMAL PURE SUBSTANCE
18 V3C2 NORMAL PURE SUBSTANCE
19 CR3SI NORMAL PURE SUBSTANCE
20 CRSI2 NORMAL PURE SUBSTANCE
21 CHI_A12 absent SUBLATTICE
22 SIGMA absent SUBLATTICE
23 AL5FE4 NORMAL PURE SUBSTANCE
24 AL3NI2 NORMAL PURE SUBSTANCE
25 ALNI_B2 absent SUBLATTICE
The remaining problem concerns the M23C6 phase. All the missing unaries
and binary interactions referred to in the diagnostics are implied by
the existence of a dataset for the unary Ni:Ni:C\
In principle, similar questions arise concerning the M3C2 and M7C3 phases. Inspection of Table 2.8.2 shows that only one unary is present for M3C2, namely number 16, Cr3C2. The user should consider whether Fe and conceivably Ni might dissolve in this phase, in which case data would be needed for the two unaries and the three binary interactions. The data for the M7C3 phase include two unaries, namely Cr7C3 and Fe7C3 and the interaction between them. There are no datasets relating to solution of Ni in this phase but this is certainly less important and the extent of solution may be negligible.
If the possible problem of the M3C2 phase is ignored, the steps needed to eliminate the difficulties are illustrated in Table 2.8.5, in which all phases unlikely to contribute are classified as absent as well as the Ni:Ni:C unary in the M23C6 phase. A list of phases and a small section of the substance list is given in the Table. The list of phases has been annotated with "-" and "?" respectively to indicate phases that are rather obviously not required and those which are known not be relevant through knowledge of the data or the physical metallurgy.
Table 2.8.5 Reclassification of phases and a unary in the Fe,Cr,Ni,C system
ACCESS OPTION ? [MISSING_DATA=CONTINUE
def sys "Fe,Cr,Ni,C" out "st1b"!
SEARCHING FOR SYSTEM Fe,Cr,Ni,C
sgsol - SGTE Solution Database 3.01 - 19/7/93
ACCESS OPTION ? classify absent phases(1,4,8,9,13-21,23-25) sub(38)!
ACCESS OPTION ? list system phases!
NUMBER PHASE STATUS MODEL
-------- --------------------- -------- ----------------
1 DIAMOND A4 - absent PURE SUBSTANCE
2 GRAPHITE NORMAL PURE SUBSTANCE
3 LIQUID NORMAL PURE SUBSTANCE
4 GAS - absent IDEAL GAS
5 BCC\_A2:1:3 NORMAL PURE SUBSTANCE
6 CEMENTITE:3:1 NORMAL PURE SUBSTANCE
7 FCC\_A1:1:1 NORMAL PURE SUBSTANCE
8 HCP\_A3:1:.5 ? absent PURE SUBSTANCE
9 KSI\_CARBIDE:3:1 ? absent PURE SUBSTANCE
10 M3C2:3:2 NORMAL PURE SUBSTANCE
11 M7C3:7:3 NORMAL PURE SUBSTANCE
12 M23C6:20:3:6 NORMAL PURE SUBSTANCE
13 CBCC\_A12:1:1 ? absent PURE SUBSTANCE
14 CUB\_A13:1:1 ? absent PURE SUBSTANCE
15 FE4N:4:1 ? absent PURE SUBSTANCE
16 FECN\_HCI:2.2:1 ? absent PURE SUBSTANCE
17 M5C2:5:2 - absent PURE SUBSTANCE
18 V3C2:3:2 - absent PURE SUBSTANCE
19 CR3SI:3:1 - absent PURE SUBSTANCE
20 CRSI2:1:2 - absent PURE SUBSTANCE
21 CHI\_A12:24:10:24 ? absent PURE SUBSTANCE
22 SIGMA:8:4:18 NORMAL PURE SUBSTANCE
23 AL5FE4 - absent PURE SUBSTANCE
24 AL3NI2:.6:.4 - absent PURE SUBSTANCE
25 ALNI\_B2:.5:.5 - absent PURE SUBSTANCE
ACCESS OPTION ? list sys subs ! note that the list has been shortened
NUMBER UNARY/SUBSTANCE STATUS SOURCE
-------- ------------------ -------- --------
36 Ni:C\<FCC\_A1\> NORMAL SGSOL
37 Ni:C\<HCP\_A3\> NORMAL SGSOL
38 Ni:Ni:C\<M23C6\> absent SGSOL
39 Cr\<LIQUID\> NORMAL SGSOL
40 Cr\<g\> NORMAL SGSOL
The diagnostics resulting from saving the data are given at the head of Table 2.8.6. As expected only one problem remains, namely the missing data for the interaction between Cr and Ni in CEMENTITE. The remainder of the Table shows the result of recovering the data into MULTIPHASE. Note that CEMENTITE is classified as absent. This should be reclassified as NORMAL before calculations are undertaken. The user should take steps to obtain good data for the interaction of Cr and Ni as soon as possible.
Table 2.8.6 Results of pruning the phase and unary list (Table 2.8.5) before saving
ACCESS OPTION ? save
SIMPLIFIED MODEL USED FOR PHASE M3C2:3:2
ERROR: NO DATA FOR BINARY INTERACTION Cr,Ni:C<CEMENTITE:3:1>
****** 1 PHASES IDENTIFIED WITH INCORRECT OR MISSING DATA ******
PHASE: CEMENTITE:3:1
ERROR: Missing data for binary interaction(s)
****** GOOD DATAFILE CREATED (but missing/inconsistent data) ******
****************************************************
* FOR MISSING INTERACTION DATA SEE FILE misbin.dbl *
****************************************************
ACCESS OPTION ? ret multiphase
MULTIPHASE OPTION ? define data "def" !
Date and time of run 6-JAN-94 12:08:46
* DATAFILE = def.mpi - CREATED 12:08 06/01/94
* SYSTEM = Fe,Cr,Ni,C,
* NUMBER OF PHASES = 9
* NUMBER OF SPECIES = 34
*
********************************
* UNASSESSED OR INCORRECT DATA *
********************************
*************************************
* WARNING/ERRORS HAVE BEEN DETECTED *
*************************************
1 Errors(s) : UNASSESSED DATA - Missing data for binary(s)
MULTIPHASE OPTION ? lis sys phases !
NUMBER PHASE STATUS MODEL
1 GRAPHITE NORMAL PURE SUBSTANCE 2 LIQUID NORMAL REDLICH-KISTER 3 BCC_A2 NORMAL SUBLATTICE 4 CEMENTITE NORMAL SUBLATTICE 5 FCC_A1 NORMAL SUBLATTICE 6 M3C2 NORMAL PURE SUBSTANCE 7 M7C3 NORMAL SUBLATTICE 8 M23C6 NORMAL SUBLATTICE 9 SIGMA NORMAL SUBLATTICE
MULTIPHASE OPTION ? lis sys subs !
NUMBER SUBSTANCE STATUS/CONSTRAINT SOURCE
1 C\
It is instructive to examine the entries in the list of substances at the foot of Table 2.8.6 (after retrieval by MULTIPHASE) and to compare them with the entries in Table 2.8.2 (before saving by ACCESS). The substances in Table 2.8.6 are in fact species on the individual sublattices rather than unaries. For example unary Ni:Cr:Fe contributes to the three species Nizl, Cr22 and Fez3, where the number indicates the sublattice. Conversely species Nizl receives contributions from unaries Ni:Cr:Fe, Ni:Cr:Ni and Ni:Cr:Cr.