MTDATA – Phase Diagram Software from the National Physical Laboratory

 

 

 

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Access

Introduction

The ACCESS module is designed as tool for the preparation of data for the calculation modules, with which it shares a common command structure. The components under study are entered, and the specified database(s) are searched for all the substances that are linear combinations of them. For even a small number of components, the number of substances could run to several hundreds and, since the calculation modules are normally configured to handle a limited number of substances, some reduction may be necessary. The databases will depend on the installation.

ACCESS allows the user:

(a)  to exclude completely some substances from the datafile to be used by the calculation modules, for example, those which are considered to be very unlikely to be significant in a particular problem.
(b)  to choose which data set is to be used for each of the remaining substances on an individual basis, rather than on a first found basis as in the preliminary database search.
(c)  to select data for solution phases that use particular models.
(d)  to identify phases likely to include miscibility gaps.
(e)  to specify non-elemental components, retrieving only those substances that can be formed from a linear combination of the stipulated components and permitting a definition of the system that is most consistent with its chemistry.

Once the status of unaries and phases for the system have been edited into a form which satisfies the user, the data can be saved to a file which can then be read by MULTIPHASE and the other calculation modules. No printed output is generated by ACCESS: a print-out of the file may be obtained, if required, via the appropriate operating system command. It is possible to edit this file manually but it is not recommended.

Brief summary of commands

DEFINE allows the user to define

(a)  the system to be studied in terms of its components, which need not be elements.
(b)  the databases from which data are to be retrieved.
(c)  the output datafile to which data will be subsequently written when the SAVE command is issued.

DEFINing the system is executive, causing the databases to be searched.

LIST displays on the screen the current status of the system in terms of which elements, substances, components and phases are present.

CLASSIFY allows the status of individual phases or substances to be classified as NORMAL (present) or ABSENT from the calculation prior to SAVEing the data for subsequent use by the calculation modules. The number of miscibility gaps potentially present may also be specified if they are to be taken into account in future calculations.

SAVE writes all data sets corresponding to substances and phases with NORMAL or MISCIBILITY classifications to a datafile specified in DEFINE OUTPUT_DATA_FILE, or to the default file if one has not been specified.

RETURN takes the user out of ACCESS back to the module level.

<"Macro name"> runs a macro taken from a file. The name of the file should be entered in quotes. Commands can also be passed through to the operating system by prefixing them with a $ (dollar sign). The dollar sign and operating system command should be entered within quotes.

[CONFIGURATION_VARIABLE not strictly an option but is of special importance in ACCESS. The setting of certain MTDATA configuration variables can modify selection criteria and the manner in which data are saved to the output_data file.

Further Information

A gentle introduction gentle introduction to using the options available in ACCESS contains annotated examples, each directed towards achieving a particular outcome, showing typical combination of commands which would be necessary to achieve that end.

A simple summary of the commands available can also be used as an index to obtain more detailed help about each command.

 

Updated 22 June 2010