Other Info

This is older unedited info from main MTDATA introduction.

Installation, customising and file management

The installation and customisation of MTDATA are covered by the System Management Guide. For data to day purposes, the user can modify operation in two main ways.

Changing the menu of databases

The mtconfig.txt file contains a menu of databases together with their aliases which can be modified by the user. The user can add to the databases using the UTILITY module and can change their priority by changing the order in which they are listed in mtconfig.txt. A text editor can be used for this purpose. Users can elect to have individual mtconfig.txt files in a number of work areas or to use the default file in the MTDATA directory

Use of MTDATA configuration variables

The mtsignon.txt file is used to initialise a number of variables that modify certain features of MTDATA. The variables can be changed from the command line of MTDATA by an entry such as [HCPY=EPS. Capitals must be used before, and in most cases, after the equals sign. The list of MTDATA configuration variables current at the time of writing this handbook is given below. When an configuration variable is changed interactively, two carriage returns may be required with no intervening prompt. In the following list the default option is given first. "blank" means that the mtsignon.txt normally contains no entry. The reader should refer to the System Management Guide and the notes provided with new versions of MTDATA for additions or modifications to the list given here.

[ATTNCHR [/<any ascii character accessible from the keyboard> 
the function supplied by [ as a prefix to configuration 
variables can be transferred to any other character by 
changing the value of ATTNCHR, for example for the 
purpose of providing compatibility with various 
keyboards. 
[TER Eg: [TER=VGA(81,900,720) indicates VGA mode 81, 900 
x 720 pixels. 
[MODE INTERACTIVE/BATCH/DEMO 
BATCH is used in macros and demo in rolling 
presentations. 
[MACRO FAIL/CONTINUE 
Macros will fail to run if they contain any error but will 
continue processing if [MACRO=CONTINUE. 
[HCPY=<option>{<init>;<close>} POSTSCRIPT/HPGL/TEKTRONIX/EPS/NONE 
the option specifies the nature of the graphics output 
file. PostScript, HPGL and Tektronix 4010 are supported 
by many types of printers and plotters. EPS is used if 
encapsulated PostScript is required. The optional codes 
<init> and <close> refer to initialisation and close codes 
needed by particular printers. 
[METAFILE blank/<name of metafile>/NUL: 
specifies the name of a text file that can be edited if 
desired and replotted by the utility module 
[BELL 20/<number of iterations between bells>/NONE 
specifies the frequency of the bell that normally bleeps 
every 20 iterations of MULTIPHASE 
[PAGE 24/<number of lines between page breaks> 
can be modified to suit the number of lines that can be 
accommodated on the screen 
[MENU VERTICAL/HORIZONTAL 
in horizontal menus the items are grouped four to a line 
[SUBLATTICE SIMPLIFY/NOCHANGE 
when a solution phase has mixing on only one 
sublattice in the chosen system the selection of 
SIMPLIFY presents the data as though there was no 
sublattice structure. 
[IMPLICIT_COMPONENT NONE/<name of implicit component> 
if, for example, IMPLICIT_COMPONENT=/­, "/­" is 
added to the system names when this is defined in the 
ACCESS or calculation modules 
[MISSING_DATA FAIL/CONTINUE 
if MISSING_DATA is set to FAIL, any missing binary 
interaction data are appended as zero to the .mpi file 
generated when data are retrieved by the ACCESS 
module and each data set is preceded by a warning line 
which must be removed for the file to be loaded by 
MULTIPHASE or the other calculation modules. If the 
flag is set to NO the missing binary data are appended 
as zeros and warning information stored at the end of 
the file. In such cases phases with missing data would 
initially be classified as absent on being read into 
MULTIPHASE or the other calculation modules. 
[ENDCHR %/<any ascii character accessible from the keyboard> 
the function of % in concatenating a line to the next can 
be transferred to any other character by changing the 
value of ENDCHR for example by entering 
[ENDCHR=&. 
[HISTORY YES/NO 
HISTORY is not strictly a configuration variable. Its 
function is to provide immediate traceability 
information. See Section 3.5. 
[DBOS (PCs only) gives a memory use report including paging 
information. 
[HLTn where n=1, 2, 3, 4 or 5. Controls text highlight codes 
used for error messages etc. 
FOREGROUND (PC only) Controls foreground VGA/EGA graphics 
n 1 n 2 n 3 n 4 n 5 n 6 colours. The six numbers should be entered on the 
following line. 
BACKGROUND (PC only) Controls background VGA/EGA graphics 
n 1 colours. The number should be entered on the following 
line. 

Files used and generated by MTDATA

MTDATA uses and generates many types of file, details of which are given below. The file names given here apply to PC versions. There will be some variations for other operating systems, which may also generate files with operating system version numbers. In these cases earlier output files are not overwritten as are some files on PCs. The location information is not rigid and in any case it is often useful to have different work areas for different projects. Further information is given in the System Management Guide. name function location permanence read.me similar in content to system management guide mtdata p sgm000.exe executable image of MTDATA mtdata p mtdata.hlp help file mtdata* p menu?? menu files, up to 16 in all mtdata* p mtdata.bat batch file for running MTDATA mtdata m mtbanner.txt MTDATA introductory screen mtdata* p mtsignon.txt User preference file work* m mtconfig.txt User database directory and aliases work* m mtsymes.txt System message file mtdata* op,m mtpermit.txt authorisation for user and organisation on a particular computer mtdata p mtstart.txt startup macro file mtdata op,u mtmode.txt selects interactive or batch operation mtdata u app*.mac resident applications (some have other root names eg scheil.mac) mtdata p ldbname.dbs database leased with MTDATA eg DEMO01, SGSUB, SGSOL mtdata p ldbname.inx database index files for ldbname.dbs mtdata p username.dbs users own databases work m username.inx indexes to users databases work m username.loa users database source files: the extension may vary eg *.dbl source m misbin.dbl file generated by ACCESS containing zero entries for missing interactions work ov *.mpi datafile generated by ACCESS: the default is def.mpi work a *.mpr results file from MULTIPHASE: rootname from .mpi file work ov *.gph graphics results file: rootname from .mpi file work a *.nbr binary results file: rootname from .mpi file work a *.tnr ternary results file: rootname from .mpi file work a

name function location permanence *.fap fitandplot input file work a *.fit fitandplot results file work a *.exp binary/gplot/ternary experimental data work a *.gky key to .gph files work a *.gtb tabulated output based on .gph file work a *.mta or *.mtf text metafile of graphics data work a isopleth.txt intermediate file generated by the isopleth application work ov adiab.txt results from adiabatic application work ov,a *.mac user generated macro file: extensions other than .mac are possible work u mt???.log log of user input for current session to provide traceability work a plot???.out graphical output file for copying to plotter or printer work a plot000.cnt counter for plot???.out files work u count.lis counter for .gph files work u count.rep counter for .tnr files work u mtlog.cnt counter for MT???.log files work u copout.dat summarised output from coplot work ov mtload.err utility module load_data error report file work ov,e trash.txt holds warning messages that could spoil a diagram work ov,e *.txt an editable text file work t *.eps preferred name for plot files in encapsulated PostScript work a Key: * files will be used that exist in the current directory, otherwise the path given by MTDATA_PREFIX will be employed or, if none has been set up, the first file encountered in the existing path. p permanent: do not delete or modify m maintain: may be modified but not deleted: retain copy of the original u user file: modify or delete at users discretion a archive before deletion, these are mostly the results from calculations e error file: contains temporary information on errors: examine if errors are detected op optional file, may be deleted, retain copy ov overwritten by later calculations. Results files are overwritten if the current .mpi file has the same root name.

Utility Software (PC only)

The management of files and other aspects of using MTDATA can be facilitated by means of established Utilities for locating text and files, for capturing screen images etc. A very incomplete list of some useful utilities is given below all but one of which (GOSCRIPT) can be obtained as shareware and used for a modest cost. These utilities may not work with all equipment; no guarantee of suitability is given. PKZIP for compressing and archiving files from PKWare Inc, available in UK from Shareware Marketing, 3a Queen St. Seaton, Devon, EX12 2NY England. Tel 0297 24088; Fax 0297 24091 SST for location and management of files, eg find and optionally delete plot*.out files for the last two days: Keith Ledbetter 4240 Ketcham Drive, Chesterfield, VA 23832, USA. CompuServe: 72240,1221 COMMANDO for retrieval and editing of previous keyed entries: Brent McPherson. SCROLLIT for scrolling over previous calculations and for capturing text information from the screen in MTDATA: Bromfield Software Products, 797 Somerset Street West, Post Office Box 57044, Ottawa, Ontario, CANADA K1R 1A1 GOSCRIPT for converting text and graphics PostScript for printing on a variety of printers: Laser Go Inc, 9369 Carroll Park Drive, Suite A, San Diego, CA 92121 USA, Tel: 619 450 4600, Fax: 619 450 9334, or major software retailers.

3 Program Structure and Operation

3.1 Module level

All modules within MTDATA share a common user interface, which is essentially command­ driven with on­screen help. User control operates at four levels of user awareness. The prompt tells the user very briefly the current level. For example at the top level the prompt asks what module the user wishes to select. The users responses here are given in italic sans serif font and are assumed to be terminated by a carriage return. Entry of a question mark gives a menu of the keywords and other user options at any point. WHICH MODULE ? ? ACCESS MULTIPHASE GPLOT BINARY TERNARY APPLICATION THERMOTAB COPLOT FITANDPLOT UNARY UTILITY VERSION EXIT The above menu appears on entry of a question mark and the prompt returns. To leave MTDATA from the module level the user enters exit. Information about the current version of MTDATA can be obtained by entry of version. Help is obtained for any one of these options by entry of the option name preceded by a question mark. For example to learn about THERMOTAB WHICH MODULE ? ?thermotab The user interface will accept any unique abbreviation. Thus in the above example WHICH MODULE ? th is acceptable but WHICH MODULE ? t is not sufficient, as the "t" could stand for THERMOTAB or TERNARY. The correct entry will cause the programme to move to the THERMOTAB module and to issue a prompt at the COMMAND level: WHICH MODULE ? th THERMOTAB OPTION ? JANUARY 1994 GENERAL INTRODUCTION  page 14 MTDATA HANDBOOK

3.2 Command Level

On entering a module, the menu of commands can be obtained by entry of a question mark, for example, for THERMOTAB: THERMOTAB OPTION ? ? AUTOBALANCE DEFINE STATUS USE_DATABASE SET STEP PLOT TABULATE AMEND SAVE_DATA LIST QUANTIFY GO RETURN <'Macro name'> Again, this menu can be displayed by entry of a question mark (section 4), and the current module is indicated by a change in the prompt, in this case to: THERMOTAB OPTION ? An appropriate response would be any of the keywords in the list or their unambiguous abbreviations. Some command keywords bring immediate response without further entry apart from carriage return. For example: In THERMOTAB, entry of go results in tabulation and/or plotting of thermodynamic functions. Entry of status yields the value of such parameters as temperature and pressure, and indicates which database(s) and substance(s) have been selected. In all modules return moves the user back from the command to the module level. Each of these keywords is typed in and followed immediately by . The majority of command keywords, however, require a series of parameters with their associated values followed by an exclamation mark ! to complete them. It is this set of modifiers which constitutes the third level of the program. 3.3 Parameter/value level Most command keywords must be followed by a valid series of parameters and values and be terminated by !. What constitutes a valid series depends upon the option selected. The stop option is always available; it is used to abort a command. The main purpose of this section is not to give exhaustive examples for each option keyword ­ details for these can be found in section 5 of the appropriate module guide ­ but to illustrate the two main styles available for entries by the user. Perhaps the easier of the two methods for beginners or intermittent users, is to allow the program to act as a guide through the entry. A typical conversation, using THERMOTAB as an example, would be: THERMOTAB OPTION ? tabulate TABULATE allows the user to define the destination of the output GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 15 TABULATE OPTION ? ? TERMINAL FILE TITLE STOP Keyword options or prompts are always available TABULATE OPTION ? terminal TABULATE AT TERMINAL, ENTER YES OR NO yes This sequence causes the output to go to the terminal TABULATE OPTION ? ! Each command sequence must be terminated by ! THERMOTAB OPTION? Other methods of obtaining on­screen help are reviewed in section 4 and a quick guide is given in section 8. A briefer form of interaction is more appropriate for the user familiar with THERMOTAB, its options and parameters. The above conversation could be replaced by one line of the format:

[ = ] ! where [] indicates allowable repetition THERMOTAB OPTION ? tabulate terminal=no ! Indeed, the system is flexible enough to take several options and parameters on one line, provided they are in the correct sequence. An example is given below which will repay further inspection, once the remainder of the handbook has been digested: THERMOTAB OPTION ? use sgsub = all ! define equation 'H2% ? + O2 = H2O' ! plot terminal=yes ! go The concatenation character % (see [ENDCHR in Section 2.2) at the end of the first line is occasionally useful because it allows more than one line on the screen to be treated as though it were only one line of input. It results in a ? character being sent as a prompt for the rest of the user's entry. Just as, at the module and command level, keywords may be shortened to an unambiguous abbreviation, so at the parameter/value level, the parameters, and if appropriate their values, may be abbreviated. Thus, in THERMOTAB: autobalance mode=decimal substance=4 ! can be shortened to: auto mode=dec sub=4 ! or even to au m d su 4 ! In the guides to each module, for the sake of clarity, abbreviations are rarely used, but this should not be taken to imply that abbreviation is not recommended. Each user develops his/her own shorthand, but a convenient rule is to abbreviate to a monosyllable, since these JANUARY 1994 GENERAL INTRODUCTION  page 16 MTDATA HANDBOOK are nearly always unambiguous, and at this level they still retain a recognizable relationship to the full form. A special mention should be made of keywords containing underscores. Generally speaking, the part of the keyword on either side of an underscore may be abbreviated, and in appropriate cases, deleted altogether. Thus in MULTIPHASE: set lgt_pressure(1)=­6 ! may be abbreviated to: set l_p(1)=­6 ! or even set _p(1)=­6 ! In this case the underscore itself cannot be dispensed with but only because LGT is not unique. Subscripted keywords The above is an example of a subscripted keyword. The subscript is bracketed and always applies to components, substances or phases. In some cases the subscripts can include multiple values. Depending on the particular function the subscripts may be numbers or character strings or in some cases either. The on­line help should be used to determine which. Where multiple values are possible entry of * or all results in the operation being applied universally. Examples are given below. classify absent phase(bcc) s(all) normal s(1­7,16) ! In the above example the BCC_A2 phase and all of the substances are removed and then some of the substances are restored. Commas and hyphens are the only delimiters allowed within the brackets. Note that bcc is an acceptable abbreviation. set n 1 n(1) 0.3 ! In a two component system the above command would set the total moles to 1 and that of the first component to 0.3. The amount of the second component would be calculated by difference. set n(CO2) 0.2 ! set n(CO2) 0.2 ! The above two examples give quite different results. In the first 0.2 moles of C and 0.4 moles of O are added to the overall system composition, in the second the final amount of CO 2 present in the gas phase at equilibrium is 0.2 moles. set n( ) 1 2 0.2 ! If the system were C­H­O, the above command would set the amounts of components C, H and O to 1, 2 and 0.2 moles respectively. The user would be prompted if insufficient values were entered. ordinate component_distribution component(Fe) ! The above command would change the graphics ordinate to the distribution of Fe between the phases. GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 17 ### 3.4 Macros A macro is a file containing exactly the same sort of commands, parameters and values as a user would enter from the terminal. The system editor could be used to make up a file like the following example in which the file is named step.mac. define data 'JET4' ! ; This line and the next two lines are "silent" comments. ; The next line removes phase 3 from the problem and ; makes phase 4 the reference phase for component 1. classify absent p(4) reference(1) 3 ! set w 1 w(2) .3 ! step w(1) .01 .69 .01 ! ; The following three comment lines will be echoed. : Calculation for 1150 K in progress. set te 1150 ! comp ! : Calculation for 1250 K in progress. set te 1250 ! comp ! : Calculation for 1350 K in progress. set te 1350 ! comp ! ; The next command will require a response from the user to ; the prompt ENTER TEMPERATURE/K : ; Exactly eight asterisks are put in the macro where input is required. ; The asterisks should be the last item on the line. set te ******** ! comp ! : ***** project terminated **** ret exit In the above example, lines prefixed by a semicolon are purely remarks; those prefixed by a colon are echoed to the screen during macro operation. Macros are particularly useful when the effects of varying the data are to be explored. Macros avoid the repeated typing of commonly repeated conditions and in this particular example the macro functions as a mini batch file, undertaking the production of a series of graph files while the operator gets on with other tasks. This particular macro begins with a multiphase command and can therefore be invoked from within MULTIPHASE by prefixing the name of the macro with an apostrophe as follows: MULTIPHASE OPTION ? 'step.mac There is a useful overlap in the functions of macros and batch operation of MTDATA. Advice on the generation and use of batch files can be found in the System Management Guide. Macros may include user defined input points, because parameters will be prompted for if not supplied on the original command line in the macro file. "Silent" and "echoing" comments may be inserted into macros. These facilities, when used together provide a mechanism for customising the user interface. A disadvantage is that user input must be completely accurate. The macro will not recover from erroneous input unless [MACRO=CONTINUE has been entered as is the case in all log files. ### 3.5 Log files By default MTDATA automatically produces a log of all user interaction and of data sources used. The log opens when the user enters MTDATA and closes on exit. Log files are generated in the directory from which MTDATA is run. They are named consecutively in the form mt123.log. Each line of user input will appear twice in the file: once prefixed by a colon to provide an echo to the screen, the other executive. JANUARY 1994 GENERAL INTRODUCTION  page 18 MTDATA HANDBOOK The log file may be used as a macro to repeat exactly what was done on a previous occasion or it may be edited to change the calculations or to prevent the macro exiting. In this case it is recommended that the mt???.log file is copied to one with the same root name but the extension .mac, so that the original log file is preserved and the macro can be easily identified. For purposes of total quality management all datafiles (those with the extension .mpi) should be preserved with the relevant .log files. If storage space is limited it may be useful to compress the files onto floppy disks or tape after each definitive session. GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 19 ## 4 Help Facilities MTDATA is well provided with on­screen help and error messages. This section does not list all of them, but attempts to provide an explanation of how to call up help at various levels and how to interpret commonly occurring error messages. ### 4.1 Menus Although there is no provision for pointing to items on the menu, it is possible to call up a list of valid keywords at each level, prior to making an appropriate response to the current prompt. This is achieved by entering a question mark. Thus, at the highest level: WHICH MODULE ? ? produces: ACCESS MULTIPHASE GPLOT BINARY TERNARY TRANSITION THERMOTAB COPLOT FITANDPLOT EXIT <'macro name'> At the command level, in for example, THERMOTAB: THERMOTAB OPTION? ? produces: AUTOBALANCE DEFINE STATUS USE_DATABASE SET STEP PLOT TABULATE AMEND SAVE_DATA LIST QUANTIFY GO RETURN <'macro name'> and at value level, in for example, MULTIPHASE LIST SYSTEM: ENTER NAME OF LIST ? ? produces: ELEMENTS COMPONENTS PHASES SUBSTANCES SETTINGS ALL In each case, the current prompt is echoed ready to accept a keyword from the list just displayed. JANUARY 1994 GENERAL INTRODUCTION  page 20 MTDATA HANDBOOK ### 4.2 Help Complementing the menus outlined above, is the help facility, which produces a fairly full explanation of the function of each word appearing in the list. These messages can be called up at module, command or parameter level, by entering a question mark followed by the keyword of interest. Thus, at the module level: WHICH MODULE ? ?multiphase MULTIPHASE Computer response : MULTIPHASE OPTION ? This is a module for the calculation of multiphase, multicomponent equilibria. Phases may include alloys, molten salts, gases, aqueous solutions, slags, mattes and pure stoichiometric substances in any combination. MULTIPHASE gives you the opportunity to ­ DEFINE a system or datafile, results file and list of databases to be searched ­ LIST various information about components, phases, substances and the settings to be used in a calculation ­ CLASSIFY a component, phase or substance as 'normal' or 'absent', a component as 'free', a reference phase for activity evaluation or a phase as having a miscibility gap ­ SET the temperature, pressure, gas volume, composition or fix equilibrium values of mole fraction, partial pressure or molality ­ STEP any of the above ­ COMPUTE the equilibrium state of the specified system ­ ORDINATE variable, axis limits and scale selection ­ ABSCISSA variable, axis limits and scale selection ­ PLOT the results of a 'stepped' equilibrium calculation ­ RETURN to select another module At the command level: MULTIPHASE OPTION ? ?step STEP This command allows the user to specify stepped values of the temperature, pressure/volume, amounts of individual components and/or substances and molalities prior to a calculation. In each case the start, final and step values are required. Examples: STEP TEMPERATURE = 300,1000 10 ! STEP X(4) = 0.1, 0.9, 0.02 ! STEP LGT_MOLALITY(H/+) = ­14,0,0.2 ! The variables that can be stepped are the same as those that can be SET (qv), except for the omission of the totals W and N. Only one variable can be stepped at a time: the latest overwrites the previous stepped variable. To unstep a variable SET a value or STEP another variable. Note, however, that THERMOTAB OPTION ? ?thermotab would produce an error message rather than help, since this keyword is relevant only to the previous level. GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 21 ### 4.3 Common Errors Two common types of user error are demonstrated here to illustrate the way the command parameter value protocol operates. Example 1: A keyword error followed by a incorrect response to the current prompt THERMOTAB OPTION ? amend eqation 'H2','H2' ! EQATION KEYWORD NOT RECOGNIZED AMEND WHAT ? "Equation" has been misspelled. A common error at this point is to repeat the whole entry: AMEND WHAT ? amend equation 'H2','H2' ! when only equation 'H2','H2' ! is expected by THERMOTAB. The result is: AMEND KEYWORD NOT RECOGNIZED AMEND WHAT ? The moral is to look carefully at the current prompt. Example 2: A missing exclamation mark THERMOTAB OPTION ? amend equation 'H2','H2' AMEND WHAT ? To execute the command a ! is needed. The message is exactly the same as if you had typed AMEND because the program allows you to amend another item or abort. Error messages from MULTIPHASE Error messages produced as a result of MULTIPHASE calculations may not always be precise. This is because a number of different types of problem may have the same effect in preventing MULTIPHASE reaching a solution. The user should think carefully about the data and the way the problem has been posed and should consult the MULTIPHASE handbook for relevant information. JANUARY 1994 GENERAL INTRODUCTION  page 22 MTDATA HANDBOOK ## 5 Databases, Definitions and Models Three main types of database/datafile are used in MTDATA. The foundation is provided by the database source files which are ascii text files identifiable by the preferred extensions .loa or .dbl. They are used as the source for generating the databases themselves each of which comprises a binary data base and an index designed for fast retrieval of data. These have the extensions .dbs and .inx respectively. Finally, when data are retrieved for a system they are transferred to another ascii file which by default is given the extension .mpi. With limited exceptions only the source files are of interest to the user, since it is to these files that all calculations are ultimately traceable. Full details are given in an Annex to the UTILITY handbook. It is possible to edit the .mpi files but this is not recommended. Users can amend and add to their own databases (.inx and .dbs files) for pure substances using the THERMOTAB module. For other purposes the UTILITY module must be used. MTDATA generates a substantial number of output and working files. Information on these relevant to their use and management is given in Section 2.3. ### 5.1 Elements, charge and vacancies Elements are represented by their normal chemical symbols using upper and lower case. Charge The electron is represented by /­ and positive charge by /+. The use of two different symbols for charge avoids the need for negative stoichiometry numbers. Vacancies Vacancies are represented by Va. They do not need to be included in lists of components when systems are defined. ### 5.2 Substances of fixed composition For the purpose of developing new data substances must conform to the following rules. The following explanations should be read in detail particularly by those concerned with the data storage or amendment. 1. Up to eight elements are allowed in one substance. 2. Normal chemical conventions are observed for the representations of symbols and formulae. 3. The phase of each substance is described by appending at least one symbol to the formula inside pointed brackets <>. The allowed state symbols are: condensed, ie liquid or solid, the default option and normally omitted, aqueous species, gaseous species ( is expanded to by ACCESS, MULTIPHASE etc but not by THERMOTAB). All constituents of solution phases and some pure substances need to be further defined by a more definite phase label, for example: Carbon C C Iron Fe Fe GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 23 If a pure substance other than a gaseous or aqueous species has no phase label one is generated by capitalisation of the formula name on data retrieval, eg MnO2 becomes MNO2. This does not apply to THERMOTAB. Isomers are distinguished by a different convention in which an isomer identifier is tagged to the formula by an underscore, eg: C2H2Cl2_1,1 C2H2Cl2_trans C2H2Cl2_cis. In THERMOTAB or in files for loading data into databases a different convention is used in which the isomer name is contained in the phase label, eg . Charged species may be represented by using the symbols for negative and positive charge exactly as if they were element symbols, ie symbol before stoichiometry number. Examples of substance names are: SnO2 Cu/+2 Fe2(SO4)3 SO4/­2 Ca2Al2SiO7 In general use of generic names for phases is recommended. Thus in the last of these examples 'melilite' is preferred to 'gehlenite'. On the other hand, if no solution data are available for mixtures with other melilites, 'gehlenite' is the better name to use. ### 5.3 Unaries Unary data are required for end members of solution phases. For this reason it is convenient to use the word unary as a noun to describe a constituent of a solution phase. A unary may be a normal stoichiometric substance that is stable in the pure state: Fe and SiO2 are examples. In other cases it may be essentially equivalent but unstable in the pure state, for example Cr. In addition to these self­evidently necessary unaries it is sometimes necessary to add hypothetical associated species that are invoked in order to model the properties of solution phases in which there is strong interaction between the components. Phases for which there is explicit recognition of sublattice structure also need to be considered and these require an extension of the formalism. Sublattices Colons are used to separate the sublattices. The formula for normal spinel MgAl 2 O 4 is written: Mg/+2:Al/+3:O/­2 normal spinel but because real spinel is partly inverse data will also be required for the notional substances: Mg/+2:Mg/+2:O/­2 charge = ­2 Al/+3:Al/+3:O/­2 charge = +1 Al/+3:Mg/+2:O/­2 charge = ­1 A combination of the last two gives inverse spinel. The four substances are the stoichiometric formulae for the end member constituents, unaries, of a real spinel of overall stoichiometric composition. In order to model the properties of spinels containing more or less MgO or Al 2 O 3 than the 1:2 ratio a third sublattice for cations and the possibility of vacancies on cation JANUARY 1994 GENERAL INTRODUCTION  page 24 MTDATA HANDBOOK sublattices may be introduced. These are also required for oxygen deficient or oxygen excess spinels. In the above examples the species Mg/+2 on the second sublattice is identified in MULTIPHASE as Mg/+2:2. This symbolism is used in the datafiles generated by ACCESS. There is no facility for identifying the individual sublattices by their structural position in the crystal lattice so care needs to be taken to maintain consistency in the order of assigning data to the various combinations. As seen from the examples above the unaries necessary to model certain phases may carry a net charge and may have vacancies on one or more sublattices. The user should refer to the ACCESS and UTILITY handbooks for further information. ### 5.4 Interactions in solution The user does not normally have to write down "formulae" identifying particular interactions in solution. The solution data are retrieved automatically by ACCESS. Unlike the unaries they are not identified in the list of substances and of course they are not assigned any mass in the results of calculation. Thus the user needs to be aware of the existence of interactions only in the development of new binary or higher order interaction data. Reference should be made to the UTILITY and ACCESS handbooks for further information. Following normal convention, mixing in a phase as a whole or on an individual sublattice is indicated by commas separating the species that are mixing. Sublattices are separated by colons in the same way as for unaries. Mixing generally occurs on only one sublattice at a time. Examples are: Fe,Ni Al/+3:Al/+3,Mg/+2:O/­2 Fe/+2,Va:O/­2 The first example is a simple solution between Fe and Ni in the liquid phase. The second relates to mixing between the last two of the unaries of spinel given above. The third example refers to interactions between ferrous ions and vacancies in wüstite, which is given the generic phase name 'halite'. It would also be necessary to consider interactions between ferrous and ferric ions and between ferric ions and vacancies. The generation of data for loading into a database needs more detailed information than is given here. Reference should be made to the UTILITY handbook. More general information on terminology is given in the Glossary (Section 9). ### 5.5 Thermodynamic models used in MTDATA The temperature and pressure dependence of the Gibbs energy and interactions between the constituents of solution phases are described by mathematical models. Those used in MTDATA are well established in the scientific literature and are supported to varying degrees by a body of data. They are incorporated in a modular way into the software and data structures. The models include: ­ A system for describing temperature dependence of either Gibbs energy or heat capacity, that has the flexibility to deal with all the equations normally used for representing the data for pure substances and their interaction in solution. GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 25 ­ The Murnaghan model for the thermodynamic data as a function of pressure. ­ The Inden model for magnetic contributions. ­ The compound energy model allowing solution on the individual sublattices of crystalline compounds. ­ The associated solution model for liquids in which there is strong bonding between the components, the bonding having a significant covalent character. ­ The two­sublattice ionic liquid model used for molten salts and other mainly ionic systems. ­ The extended Redlich­Kister model for predicting the multicomponent thermodynamic data of non­ideal solutions including those on individual sublattices. ­ An extended Kapoor­Frohberg model for slags. ­ The Quasi­chemical model ­ The Pitzer model for aqueous solutions JANUARY 1994 GENERAL INTRODUCTION  page 26 MTDATA HANDBOOK ## 6 User Handbooks There is a user handbook for each of the modules outlined in section 1. Each has the same format: 1. Overview ­ An introduction to the module, including the main keywords and their functions, together with the main facilities which the module provides. 2. Worked Examples ­ A series of examples which illustrate the way in which the keywords could be used in real situations. Each example consists of actual output from the program with accompanying explanatory text. It is intended that this section should be studied before a workshop, but does not require access to the running program. 3. Exercises ­ A series of problems which might, for example, form the basis of a workshop or training course. Solutions are provided separately. 4. Option Definitions ­ A reference section which contains the most complete description of the function of option keywords available, together with examples and suggested uses. 5. Quick Reference ­ An abstract of the main operating features of the module. GENERAL INTRODUCTION JANUARY 1994  MTDATA HANDBOOK page 27 ## 7 Current limitations on the use of MTDATA THERMOTAB 1. Calculations cannot be made for temperatures below 298.15K. 2. Calculations can be made only with pure condensed phases, ideal gases and aqueous species represented in Cp format (see UTILITY handbook for definitions of data formats). 3. Database datasets for non­ideal solutions, sublattice phases and pure substances represented in G­Hser format may be LISTed and SAVEd but not AMENDed. ACCESS 1. The maximum number of components is normally 30. 2. The maximum number of phases is normally 500. 3. The maximum number of unaries in any one retrieval is normally configured to 1000. 4. The maximum number of binary and ternary interactions is not an exact number. The limit depends on a number of factors. Lower or higher limits to items 1 to 4 may apply for special purposes. 3. The MODEL field (LIST SYSTEM PHASES !) does not indicate solution phases until after a SAVE command has been given. MULTIPHASE 1. A maximum of 500 unaries is normally allowed. 2. The STAGE_2 equilibrium calculation is unsuitable for systems including slags and phases having multiple sublattices. STAGE_1_PLUS can be used for these systems. 3. A maximum of 1000 equilibria can be analysed by the graphical post­processor (PLOT). A much smaller number is likely to be sufficient. COPLOT 1. Only pure condensed, ideal gas and aqueous phases are allowed. 2. Calculations can be performed only at constant volume. JANUARY 1994 GENERAL INTRODUCTION  page 28 MTDATA HANDBOOK ## 8 General quick reference guide Starting MTDATA and selecting a module RUN MTDATA by entry of MT, MTDATA, XMT or XMTDATA Enter a module name to select one of them or ? to obtain a MENU of module names. Operating MTDATA At the prompt select a COMMAND keyword of which there are two sorts: ­ those that are intrinsically executive e.g. RETURN ­ those that require further entry of parameters and values and are completed with an exclamation mark, in the form: COMMAND PARAMETER = VALUE ! Keywords may be abbreviated provided the abbreviation is unique. Three delimiters are used, namely space, comma and equals sign. The equals sign is useful for indicating assignment of values to parameters, for example SET N(CO2)=2.35 !. Within character data, i.e. data entered between quotes, spaces, commas and equals signs may have special meanings. Underscores are used to join parts of keywords, for example lgt_pressure. If the first word is not unique, the underscore must be entered, for example l_p. Menus containing indicate the need to enter numeric data Menus containing <'ITEM'> indicate the need to enter character data between double or single quotes. Menus containing keyword(*) indicate the need to identify components, substances or phases either using a number or set of numbers or unique characters: eg phase(2­4,6) or phase(liq). The items in the brackets are separated by commas or by hyphens in the case of groups. Any valid sequence of module names, commands, parameters and values can be entered on a single line or multiple lines concatenated by a % sign. HELP on any keyword is obtained by entering ?keyword with no intervening space. A carriage return will always produce a prompt. Prompts are not printed if user entries are made on a single line or if lines are concatenated by a % sign. To change a configuration variable enter eg [HCPY=EPS, see section 2.2. RETURN is used to leave a MODULE EXIT is used to leave MTDATA ; or : in column 1 indicate the start of respectively a silent or echoed comment ```