MTDATA – Phase Diagram Software from the National Physical Laboratory

 

 

 

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DEFINE

Function:

allows the user to define:
(a)    the system in terms of elemental or non-elemental components and the order in which these are subsequently presented
(b)    the databases from which data for a given system are to be retrieved
(c)    an output datafile to which the data will subsequently be written when the SAVE command is issued.

Parameters:

output_data_file

system

source

Defaults:

output_data_file = <"def.mpi">

source = <first database on the database menu>

Examples:

define output="jet4" !

define system="Mo,Si,O,N" source=sgsub mydata !

define system="Fe,H2O,H/+,/-" !

define system="KCl,ZnCl2" output="kzc" !

define source=none_but mydata !

Parameter values:

OUTPUT_DATA_FILE  takes the values <"filename">

The default filename is def.mpi and the default extension is mpi but both the name alone or the name and extension may be supplied by the user. Unless the default output file is to be used this must be specified at the same time or after the system is defined.

SYSTEM takes the value <"component list">

The SYSTEM parameter is used to define the components of the system to be studied. Elements, compounds and ionic species may be defined as components in the form of a list in quotes with the individual components separated by commas. The components should be chosen to be compatible with the models for the phases involved as this may have important consequences in subsequent calculations. The order in which the components are defined is retained in the output datafile and is thus effective in the calculation modules. Refer to Section 2 for guidance regarding systems involving charge as a component. The two examples shown below would normally give very different results.

define system="Al,Ca,Si,O" !
define system="Al2O3,CaO,SiO2,O/-2" !

SOURCE takes the values <database list>/NONE_BUT<database list>/ALL

In each case, the program searches the list of databases for substances that are linear combinations of the components defined in SYSTEM. If a value for SOURCE is not specified at the same time as the system, only the last used database list (or if none has been used the first database) in the menu is searched.

<database list>

a user-defined list comprising any of the databases appearing in the database menu in order of priority, as exemplified below.

define system "Pr,Cl,H" source sgsol mydb !

ALL this specifies the complete list of databases in the order in which they appear in the database menu.

NONE_BUT<database list>

clears any previous list of sources and defines a new one. NONE_BUT must be used if the number of databases to be searched is reduced.

General comments:

Each of the parameters may be assigned a value in a different DEFINE statement: only DEFINE SYSTEM is executive - it causes the database search(es) to be performed.

Data are not written to an output file as part of the DEFINE SYSTEM statement: there is a separate command - SAVE - which performs this operation. However, SAVE writes to the output datafile that was DEFINEd before the SAVE operation. The default output datafile is def.mpi.

A search of the first database on the list of sources will probably locate the majority of substances generated from the list of components entered under SYSTEM. Substances located in this way for the first time are retrieved into memory and flagged as NORMAL - i.e. present. The search of the next database will locate data sets of two types:

(a) data for substances which have been located for the first time are added to those in memory and similarly flagged as NORMAL.

(b) data for substances which have already been located in the search of the first database are also added to those in memory, but are flagged as ABSENT.

CLASSIFY allows the user to adjust this preliminary classification and to flag phases as likely to include miscibility gaps. SAVE causes only those substances CLASSIFY'd as NORMAL to be SAVEd.


 

Updated 24 June 2010