MTDATA – Phase Diagram Software from the National Physical Laboratory

 

 

 

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Binary

Introduction

The BINARY module allows binary (T-x) phase diagrams (ie for systems with two components) to be calculated and plotted at a fixed pressure. The user may carry out calculations for a wide range of systems such as alloys, molten salts, slags and mattes.

Calculations are normally initiated through a special graphical user interface. As the calculations proceed the diagram is plotted on the screen. Calculated invariant temperatures are displayed in a box to the side of the diagram. After the calculations have been completed portions of the diagram may be labelled interactively. The results of the calculations are stored in a form which allows replotting of the whole or portions of the diagram. Stored experimental data may be superimposed on the calculated diagram.

Data for the calculations are retrieved either from specified databases or from a datafile prepared in advance. This datafile would normally have been generated from the databases by means of the ACCESS module. The databases will depend on the installation; those that may be available include:

UNARY

Recommended data for the elements

SGSUB

Scientific Group Thermodata Europe database for substances

SGSOL

Scientific Group Thermodata Europe solution database

SALTS

NPL Database for salt systems

to which may be added private or specialised databases managed by individual users or groups.

Output can be produced in tabular or graphical forms and sent both to the screen and to a file and hence to a printer.

The module requires the specification of either the names of the two components and a source database or the name of the datafile containing the thermodynamic data for the system. After fixing the pressure and range of temperatures and a step size for the calculations, a starting composition and temperature is entered by manually positioning the graphics cursor and depressing "F" or "f" to initiate the calculations. Calculation and plotting of the phase diagram then proceeds automatically and the temperatures of any phase transitions found are written in a box to the right of the diagram.

The numerical results of the calculations are stored in a file with an extension ".nbr". This allows diagrams to be replotted with any available experimental data superimposed.

Brief summary of commands

DEFINE allows the user to name the datafile from which the data are to be retrieved or to define the system to be studied in terms of the two components, in which case the data are retrieved from a named database. The datafile must be in the MTDATA Multiphase format (file extension ".mpi") and should preferably have been retrieved in advance by means of the ACCESS module.

LIST displays the current definition of the problem in terms of:

(a) the status of the elements, components, substances or phases present
(b) the pressure, temperature range and temperature step interval for the calculations set by the user.

CLASSIFY allows the status of individual phases or substances to be classified as NORMAL (present) or ABSENT from the calculation. The number of miscibility gaps potentially present may also be specified if they are to be taken into account in the calculation.

SET allows the user to specify the pressure and also a starting composition and temperature which can be used as an alternative to the cursor, from which automatic calculation of the phase diagram can proceed.

STEP allows the user to specify the start, finish and step size for temperature to be used for the calculations.

COMPUTE draws temperature and composition axes and annotation on the screen. If a starting temperature and composition have been specified with the SET command, calculation of the phase diagram proceeds automatically. Otherwise the cursor appears and a starting point within a two phase field may be selected manually. Depressing "F" or "f" initiates the automatic computation and plotting of the binary phase diagram within the range of temperatures specified in STEP TEMPERATURE. Output is sent simultaneously to the screen and a graphics file. Hard copy output can be obtained by using the command LASER which copies the contents of this file to your local plotting device.

REPLOT allows a diagram to be replotted from information stored in a binary results file (file extension ".nbr") created during a previous phase diagram calculation. A selected area may be chosen from the diagram for replotting by use of the ORDINATE and ABSCISSA commands, or else the whole diagram may be replotted. Experimental data or other annotation in a file may be superimposed.

ORDINATE allows the temperature range to be defined, used when replotting the calculated binary phase diagram.

ABSCISSA allows the composition range to be defined, used when replotting the calculated binary phase diagram.

LASER sends a copy of any diagrams plotted on the screen to a local plotting device if available.

RETURN takes the user out of BINARY 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.

Further Information

A gentle introduction gentle introduction to using the options available in BINARY 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.

Experimental data can be overlayed onto calculated binary diagrams.

 

Updated 21 May 2010