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Overview of MTDATA
MTDATA
comprises a suite of related modules which retrieve thermodynamic data
from databases and perform specified calculations on the data. The
databases may be provided with the package or maintained by the user. A
summary of the functions of some of the modules is given below.
An important feature
of MTDATA is the maintenance of a system of
traceability that is compatible with total quality management. For this
purpose a log is maintained of all user interaction.
Words such as element,
component, substance, compound, species, condensed, phase and solution
will be encountered frequently. For detailed understanding of these
terms please consult the glossary and information about databases, definitions and models.
It is possible to
assign values to a range of settings that apply across the whole of
MTDATA and affect a number of ways in which MTDATA appears or the
accuracy of the calculations. These are called "Configuration
Variables" and are assigned through use of "[" followed by the
appropriate variable name. A list of the most important Configuration
Variables can be obtained here.
UTILITY
The MTDATA
package includes a number of utilities for creating, loading and
listing databases. Facilities are also incorporated for personalising
access to particular databases and for customising graphics output. The
box shows, as an example, part of a source datafile to be incorporated
into a database by UTILITY.
Cr/+3,Ni/+2:Va<LIQUID*>
E/J
***
GEX(REDLICHKISTER) DATASET FORMAT ***
298.150 2
2
1.2760000E+03
5.3873000E+00
2
2.6990000E+03
0.0000000E+00
3000.00
0 0
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ACCESS
The ACCESS module is
designed to be used as a data retrieval system for MULTIPHASE, GPLOT,
BINARY, TERNARY, APPLICATION and COPLOT, with which it shares common
features. The components, which may be elements, compounds or charged
species, are entered and the databases are searched for all the
substances which might be present
in the system at equilibrium. In a large system this could run to many
hundreds of substances, many of which may not be very relevant to a
particular application and may therefore be excluded. ACCESS allows the
user to remove these substances from consideration completely, and to
choose from which databases the data for the remaining substances are
to be retrieved on an individual basis. There may also be a need to
select from alternative models for
solution phases. Once the data for the system have been edited into a
form which satisfies the user, they can be saved to a file which can
then be read by the calculation modules for subsequent processing.
ACCESS OPTION ? define system 'Fe,Cr,Ni,C'
source sgsol !
SEARCHING FOR SYSTEM Fe,Cr,Ni,C
SEARCHING DATABASE(S) : SGSOL - SGTE Solution Database 3.0
2/2/93
ACCESS OPTION ? list sys phases !
The list has been greatly abbreviated
NUMBER PHASE STATUS MODEL
3 LIQUID NORMAL REDLICH-KISTER
4 GAS NORMAL IDEAL
GAS
5 BCC_A2:1:3 NORMAL SUBLATTICE
6 CEMENTITE:3:1 NORMAL SUBLATTICE
7 FCC_A1:1:1 NORMAL SUBLATTICE
8 HCP_A3:1:.5 NORMAL SUBLATTICE
10 M3C2:3:2 NORMAL SUBLATTICE
11 M7C3:7:3 NORMAL SUBLATTICE
12 M23C6:20:3:6 NORMAL SUBLATTICE
22 SIGMA:8:4:18 NORMAL SUBLATTICE
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MULTIPHASE
MULTIPHASE 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 combination. Calculations may be made at
constant pressure or volume with a fixed system composition;
alternatively, constraints
may be placed on the equilibrium system in terms of variables such as
mole fraction in a phase, partial pressure and molality.
Data for the calculations are read either from specified databases, or
from a previously prepared datafile; this may be precompiled by using
the ACCESS module.
Output, in the form of tabulated equilibrium
amounts and mole fractions of each of the substances present at
equilibrium, for
each of the temperatures specified, is sent both to the terminal and to
a file. Graphical output can be invoked from within MULTIPHASE in order
to plot the amounts, mole fractions, partial pressures, component
partition between phases and activities as a function of stepped or
dependent variables. Results may be presented in mole or weight terms.
THERMOTAB
The main function of THERMOTAB is to act as the
user interface to the internal database management system of MTDATA.
At
present all data can be inspected but calculations involving equations
are available only for pure substances, gases and dilute aqueous
species. The UTILITY module should be used for data management for
solution phases. UNARY, GPLOT and MULTIPHASE can be used to obtain
tabulations and plots.
Fe3O4 + 3
H/+<aq> = 1/2 O2<g> + 3
Fe(OH)/+<aq>
T Delta
Cp Delta
H
Delta S Delta
G Beta
K J/K
mol J/mol
J/K
mol J/mol -DG/RTln10
298.15 13.277 1.48680E+05 133.27 1.88413E+05
33.008
373.15 10.914 1.49606E+05 130.49 1.98297E+05
27.758
473.15 0.21007 1.50253E+05 128.90 2.11243E+05
23.320
573.15 22.630 1.49241E+05 130.77 2.24193E+05
20.432
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THERMOTAB provides output of the Thermodynamic
functions Cp, S, G, H, Phi = -(G-H)/T and Beta = -G/RTln10, over a
range of temperatures specified by the user, for pure substances or for
chemical reactions between pure substances. The output can be produced
in tabular or graphical form, and may be displayed on the screen or
saved to a file. Hard copy can be obtained by routing the file to a
local or networked printer. The module also allows
data to be copied from the reference databases provided, modified by
the user, and used to compile private or specialised databases.
UNARY
UNARY is used in data development, for example the
provision of data for a liquid below the melting temperature of the
pure substance. It is also useful in the graphical comparison of data
from different sources or different phases.
GPLOT
GPLOT is used mainly for plotting but also for
tabulating thermodynamic functions of phases of all types. The main
application lies in the development of data for binary systems which
can include systems between compounds.
BINARY
The BINARY module is used for the calculation and
plotting of binary phase diagrams, mainly as an aid to data assessment
and
validation. The data are retrieved in the same way as with the ACCESS
module. The user sets up the calculation by specifying
the temperature range and he may subsequently select parts of the
diagram for closer inspection. Labelling of single or two
phase regions is very simple. Key information on phase boundaries is
given numerically and hard copy can readily be obtained.
TERNARY
The TERNARY module is used to plot ternary phase
diagrams. Data may be retrieved directly databases or from a datafile
compiled
using the ACCESS module. The user may optionally specify a starting
point on the ternary diagram for the calculations to begin; thereafter
the computations required for the graph to be plotted can be entirely
automatic. The diagram can be in weight or mole fraction. Areas can
readily be labelled and diagrams reorientated.
APPLICATION
APPLICATION allows the core phase equilibrium
calculation facility of MTDATA to be used for a variety of purposes
including calculating arbitrary sections through systems, finding the
temperatures of phase transitions for individual compositions and the
preparation of Scheil plots. The facility is provided for users to
develop their own process modelling software for linking to MTDATA.
COPLOT
COPLOT is used for plotting predominance area
diagrams (also called Pourbaix and phase stability diagrams) for
systems of stoichiometric substances and up to 10 components. The
potential of two of the components are the independent axis variables,
others may have fixed potentials and at least one component is
specified by amount. The output comprises a plot showing the fate of
this or these component(s) as a function of the remainder. This type of
plot is much used by corrosion scientists and hydrometallurgists.
FITANDPLOT
FITANDPLOT is used for fitting compiled
thermodynamic data to user defined mathematical functions. It
incorporates checking
for typing errors and can also be used for converting data already in
the form of an equation to a different function.
ASSESSMENT
The ASSESSMENT module provides
tools to help in the task of deriving values for thermodynamic model
parameters, which, when used as a basis for phase equilibrium
calculations, give the best possible representation of a collection of
experimental measurements obtained for a particular chemical system.
This overall task of gathering data and generating values for
parameters is referred to as data assessment or sometimes critical
assessment since it involves comparing data of many different types,
from many different sources, obtained using many different experimental
techniques. The specific task of generating model parameters
appropriate to a set of experimental data is called optimisation.
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