allows the user to define the system to be
studied: in one mode, the data are retrieved from specified databases
or from a previously compiled file. When a database search has been
performed, the data for the system under study are written to a
user-defined or system default file.
<first database on the database menu>
data = "fecrmo" !
system = "Al, Si, Zn" source = unary sgsol !
data = default !
system = "Al2O3, CaO, SiO2, O/-2" !
system = "Fe, Cu, Ni" output = "mydata" !
system = "KCl,CaCl2,ZnCl2" source = "db-salts" !
If the DEFINE
statement contains a reference to a
DATA_INPUT_FILE the program reads the required data from the specified
datafile. Such a datafile could have been created in a previous
run of MULTIPHASE or ACCESS.
If DATA = DEFAULT is used, then the data are read from the last
datafile generated with the default name.
takes the value
specifies the root for two
a) a file with
the extension ".mpi"
to which the data resulting from the database search are to be
b) a single file with
to which certain MULTIPHASE diagnostic information
If a system is to be
defined this parameter should
be used in the same DEFINE statement that contains the SYSTEM
specification. Use on its own at any other time will automatically
load in data from the default data input file ("def.mpi").
If no output file root is defined then the data are written to
a results file whose name is based upon the root of the data input
OUTPUT_DATA/RESULTS should not be confused with the file that contains
the results of TERNARY
calculations. The names of these TERNARY
results files are based on the root of the data input file name with
the filename extension ".tnr".
takes the value <"component
The SYSTEM parameter
is used to define the components
of the system to be studied prior to the search of one or more
databases. Components may be elements, compounds or charged species.
The best choice of components will depend on the models used to
represent the thermodynamic data. Details as to how components
may be specified can be found in the information to the ACCESS
DEFINE SYSTEM causes
the program to search the list
of databases specified by use of the SOURCE parameter, for the
substances that are linear combinations of the components DEFINEd.
These are written to a datafile based upon the OUTPUT_DATA/RESULTS
file root and then loaded into memory.
takes the values ALL/ <database
list>/ <"database path">/ NONE_BUT<database
This defines the
databases to be searched in the
specified order. It is recommended that the SYSTEM and SOURCE
parameters are set within the same DEFINE statement. If the SOURCE
parameter is assigned a value before a DEFINE SYSTEM command is
issued the default data input file is also loaded. If a value
for the SOURCE parameter is not specified the first database in
the database menu is searched when the SYSTEM is defined.
a user-defined list
consisting of any of the databases
appearing in the database menu.
the path of a database
not on the database list.
ALL this specifies the complete
list of databases in the order in which they appear in the database
clears any previous
list and defines a new one.
When the DEFINE SYSTEM
command is executed, the databases
specified by use of the SOURCE parameter are searched in the specified
order for all the substances that are linear combinations of the
components defined by the SYSTEM. For complex systems,
the number of substances retrieved may easily run to tens, if
not hundreds, of species representing many distinct phases. It is,
however, unlikely that a binary system will require more than 500
substances and 250 phases for which the TERNARY module is
normally configured. If the number of substances
than can be supported it
practice to use the ACCESS module to perform a
screening of species and phases before saving. This may then be read by
the TERNARY module
the DEFINE DATA command.
One problem that
may arise when retrieving data from the database searches
is that MTDATA
may identify that certain phases have missing data. Typically this
would indicate that for these phases the database contains data for the
pure components but no interaction data between them. Under most
circumstances these phases would be classified as ABSENT (ie not taking
part in the calculations) following the database search.
Another problem that
asises from the database searches is that of duplicate data sets. A
search of the first database
on the list will probably locate the majority of datasets generated
from the list of components defined by the SYSTEM. Substances
located in this way for the first time are added to the MULTIPHASE
DATAFILE and flagged as NORMAL - i.e. present. The search of the
next database on the list will locate data sets of two types:
(a) those for
substances that have been located for
the first time. Data for these substances are written to the file
and flagged as NORMAL - as before.
(b) those for
substances that have already been located
in the search of the first database. Data for these substances
are not written to the file.
The same strategy
applies to interaction between
substances. This strategy of writing data sets to the file only
for those substances that are located for the first time, ie those
that have been classified as NORMAL, means that very few data
from databases low in the database list will be retrieved. If
you wish to select datasets for substances on an individual, rather
than on a first-found basis, then again you should use the ACCESS
module to produce the datafile which can be read in via the DEFINE
A relationship exists
between ACCESS and TERNARY in terms of
the datafiles that are generated. The purpose of using ACCESS
is to perform a preliminary
review of the data and
to enable phases and/or substances to be excluded from the MULTIPHASE
input data file created so that it is suitable, in size and form,
for use by TERNARY
and other MTDATA
The recommended method for terminating an ACCESS
is to define the name of a file to which the edited data may be
SAVEd and then to issue the SAVE command. At a later date the
file may subsequently be read by the DEFINE DATA statement in TERNARY.
If such a filename has not
been defined within
the ACCESS module when the SAVE command is issued,
data are SAVEd to a default file. These data can be retrieved
by the command:
This procedure is to
be recommended only if the ACCESS
modules are used subsequently within
same session of MTDATA. Otherwise, the default
is in danger of being overwritten