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MALT2
Materials-oriented Little Thermodynamic Database for Personal Computers

• ABSTRACT
• Contents of Database
• Operation with pull-down menus
• Hardware and software to be needed

  option

• gem, Chemical equilibrium calculation program for MALT2
• CHD, program of constructing chemical potential diagrams for MALT2

Thermodynamic considerations are indispensable whenever the information is required for materials behavior in the fields of developments of new advanced materials, corrosion, metallurgy, waste management etc. If you do not have proper thermodynamic data, you could not make any fruitful analysis on such problems.
MALT2 is a comprehensive database for personal computers which makes it easy to retrieve the thermodynamic data required. In addition to retrieval functions, new thermodynamic data can be input by users and stored to make a combined set of data. Using these data, the thermodynamic properties and the equilibrium constants can be calculated without any difficulties.
The most important feature of having the thermodynamic database in personal computers is that it is realized to provide the thermodynamic environment in computers. This is a function of making it possible for users to make full use of retrieved data in their own computer programs by making MALT2 and related data memory-resident. Under such an environment, users can gain insight easily into the most important aspects of materials problems using a large number of thermodynamic data.
The task group of the thermodynamic database was organized in the Japan Society of Calorimetry and Thermal Analysis and the previous version of MALT was their first fruit. MALT2 is a new version of MALT. We believe that it will helpful for many people who have been engaged in applications of thermodynamics.

MALT2 stores thermodynamic data such as the standard enthalpy change forformation, DfH(298.15 K), the standard Gibbs energy change for formation, DfG(298.15 K), the standard entropy, S(298.15 K), the heat capacity, Cp, and the transition temperature and the enthalpy change for transition, if any, for 4931 species; this covers those compounds important to ceramic materials, semiconductors, inorganic / organic gasses for plasma processes in semiconductors, transition metal oxides, nuclear fuels, nuclear reactor materials etc. From such stored data, the thermodynamic tables and the equilibrium constants at any temperatures can be calculated. In addition, molecular mass, coefficient of heat capacity equation, and references for data can be also available.

* Point 1. Retrieve can be made by inputting directly the chemical formula and also by using other three retrieve modes which select a set of compounds by using a combination of elements. This makes retrieval easy and also fast significantly.

* Point 2. References for this system will be available on CRT; intelligent on-line help will make it easy to learn how to operate this system.

* Point 3. Many practical unit such as cal, C, kg, mN³, are available in addition to SI units of Joule, K, mol.

* Point 4. Results of retrieving data and of calculating can be saved in a file and can be read from the file again.

* Point 5. Calculation at any temperatures can be made so that there is no need to do troublesome interpolation.

Realization of thermodynamic environment by using memory-resident technique.

MALT2 provides a function of transferring the retrieved data to user's programs which are running as a child process after MALT2 together with the retrieved data in the main memory was made memory-resident. The interface with user's programs is realized by software interrupt technique from the application side. For this purpose, sample programs are provided together with subroutines or procedures for the interface. The following information can be made access to;

1. chemical formula and name, the temperature range for validity of data, information of phase (gas or condensed phase);

2. compositional information, molecular weight

3. transition temperature and enthalpy change for transition

4. the following thermodynamic functions at a selected temperature

        DTH(T) =[H(T)-H(298)]
        D'fH(T)=DfH(298)+[H(T)-H(298)]
        Cp(T)
        S(T)
        D'fG(T)=DfG(298)+[G(T)-G(298)]
   

1. Point 6. To facilitate the utilization of software interrupt technique by users, sample programs with sources written in
2. Quick Basic
3. C
4. Pascal
5. are included.

computer and OS	NEC 9801	MS DOS 3.1 or higher
	EPSON PC 286/386	MS DOS 3.1 or higher
	Fujitsu FM 16b, FMR 60/70	MS DOS 3.1 or higher
	IMP PC/AT	DOS J5.0/V or higher
memories	more than 250 kbyte
harddisk	MALT2 needs about 2.7 Mbyte in hard disk
display	640 x 400 dot 1020 x 740 dot
printer

The program, gem, is to obtain the minimum point of the total Gibbs energy of a system, or the total Helmholtz energy of a system and to give one equilibrium state together with equilibrium compositions and an associated enthalpy change. Any compounds stored in MALT2 can be used in calculations, in which gaseous species are treated as an ideal gaseous mixture, other condensed phases being as invariant compounds. Any systems containing up to 10 elements and 300 species can be calculated.

Functions
Gibbs energy mode : to obtain the equilibrium composition and related enthalpy change under a given temperature at a selected constant pressure.
Helmholtz energy mode : to obtain the equilibrium composition and related enthalpy change under a given temperature at a selected constant volume. (When the Helmholtz energy mode is selected, the equilibrium point can be obtained even for a case where the partial pressure of a selected species is fixed).

Merits
Highly convergent : because of adoption of gradient projection method combined with linear programing method, gem can give a correct solution with high convergence. (Even so, there are some cases in which the proper solution does not come to convergent because a true solution is very close to the phase stability border.)
Easy to handle : The thermodynamic properties to be needed in calculation are automatically obtained from MALT2 after a set of compounds were selected in MALT2 and gem is run as a child process of MALT2. Therefore, what users should do is the selection of temperature, pressure(volume) and mole number of reactants. That is all to obtain a result of calculation.
Utilization of user's data : MALT2 provides a function of registering user's own thermodynamic data of compounds. With an aid of this function, user's evaluated data can be used in calculations.

---------------GIBBS----------------------------CONVERGED--------
Projectedgradient:1.7123D-08Potential:Definite
TEMPERATURE(K):1273.00PRESSURE(atm):1.0000D+00
�@
COMPOUNDNAME		INITIAL(mol)		LAST(mol)	ACTIVITY
13	SO2	g	1.0000D+01	5.5018D+00	9.0152D-01
5	S2	g	0.0000D+00	5.3961D-01	8.8419D-02
15	S2O	g	0.0000D+00	5.1071D-02	8.3684D-03
6	S3	g	0.0000D+00	6.0292D-03	9.8793D-04
12	SO	g	0.0000D+00	4.2812D-03	7.0150D-04
7	S4	g	0.0000D+00	2.1773D-05	3.5677D-06
8	S5	g	0.0000D+00	1.0694D-05	1.7522D-06
14	SO3	g	0.0000D+00	4.3302D-06	7.0953D-07
4	S	g	0.0000D+00	3.2486D-06	5.3231D-07
9	S6	g	0.0000D+00	8.2249D-08	1.3477D-08
10	S7	g	0.0000D+00	1.9821D-09	3.2478D-10
18	FeS	g	0.0000D+00	3.6055D-10	5.9080D-11
2	O2	g	0.0000D+00	1.7307D-10	2.8359D-11
11	S8	g	0.0000D+00	4.4347D-11	7.2665D-12
16	Fe	g	0.0000D+00	5.5220D-12	9.0481D-13
1	O	g	0.0000D+00	3.4743D-12	5.6929D-13
17	FeO	g	0.0000D+00	7.4903D-13	1.2273D-13
21	CrO2	g	0.0000D+00	1.0224D-14	1.6753D-15
23	CrS	g	0.0000D+00	1.5303D-15	2.5076D-16
20	CrO	g	0.0000D+00	2.0285D-16	3.3238D-17
22	CrO3	g	0.0000D+00	1.8661D-16	3.0577D-17
19	Cr	g	0.0000D+00	1.1542D-17	1.8913D-18
3	O3	g	0.0000D+00	3.2770D-25	5.3697D-26
			TOTAL	6.1029D+00	1.0000D+00
�@
32	FeS troilite	c	0.0000D+00	3.2943D+00	1.0000D+00
30	Fe3O4 magnetite	c	0.0000D+00	1.7352D+00	1.0000D+00
44	FeCr2O4 chromite	c	0.0000D+00	5.0000D-01	1.0000D+00
31	Fe0.877S pyrrhotite	c	0.0000D+00	0.0000D+00	8.1890D-01
27	Fe0.947O	c	0.0000D+00	0.0000D+00	4.1776D-01
28	FeO	c	0.0000D+00	0.0000D+00	2.9985D-01
40	Cr2O3	c	0.0000D+00	0.0000D+00	1.1102D-01
29	Fe2O3 hematite	c	0.0000D+00	0.0000D+00	9.8939D-02
26	Fe	c	9.0000D+00	0.0000D+00	1.9830D-03
42	CrS1.17	c	0.0000D+00	0.0000D+00	8.7722D-05
41	CrS	c	0.0000D+00	0.0000D+00	9.9348D-06
37	Cr	c	1.0000D+00	0.0000D+00	7.9512D-10
36	Fe2(SO4)3	c	0.0000D+00	0.0000D+00	3.3599D-26

H1 (kJ)	H2 (kJ)	DELTA-H(kJ)	Cp-system(J)	DELTA-G(kJ)	VOLUME(litre)
-2.1071D+03	-3.6112D+03	-1.5042D+03	9.9615D+02	-8.2556D+02	6.3750D+02
-----------------------------------------------------------------------------

The following facilities are required to run gem

computers	NEC PC9801, DOS/V except for high resolution mode
required memory size	640 kb
required software	MALT2

Chemical potential diagrams have been utilized mainly in the fields of hydrometallurgy, pyrometallurgy, corrosions etc. This shows graphically what chemical form will be stable when materials are placed under a particular chemical environment in terms of the thermodynamic variables such as temperature, oxygen potential, and partial pressure of carbon dioxide. Since the thermodynamic information is condensed into one diagram, this can be used as a useful tool for thermodynamic application to practical problems in which reactivity and chemical stability of materials are the main issue in fields other than the above mentioned ones. So far, there is few applications using the chemical potential diagrams. This is not because of a lack of usefulness of this diagrams but just because it has been troublesome and tedious to construct the chemical potential diagrams for the multicomponent systems and also because it was difficult to draw the diagrams for the systems which contain more than two metallic elements. CHD provides a method of drawing a generalized diagram without any troublesome tasks.

Functions
* construction of two dimensional chemical potential diagram for ternary systems
* construction of three dimensional chemical potential diagram for ternary systems
* construction of two dimensional chemical potential diagram for systems containing n elements up to 6 elements under the fixed chemical potentials of (n-1) species.

Merits
* CHD can draw a chemical potential diagram automatically without any difficulty.
* Since CHD should be run as a child process of MALT2, the thermodynamic data stored in MALT2 can be used directly to draw a diagram.
* This program can construct a generalized diagram of any systems which contains metallic elements and non metallic elements.

Algorithm
This program is based on a so-called polygon method. For example, when three phases coexist in a ternary system, the chemical potentials of three elements can be uniquely determined. A stability region of a compound is represented in terms of such points in a chemical potential space. This program adopts a generalized way of determining this three-phase points so that there is no restriction on its application. Although normal chemical potential diagrams are limited for the metal-nonmetal-nonmetal systems, CHD can apply to the metal-metal-nonmetal, metal-metal-metal systems and also can extend to higher systems.

Chemical potential diagrams are quite useful for the following cases.

(1) When you want to know the stable chemical form under various chemical environments.
Drawing an appropriate chemical potential diagram will provide the thermodynamic information about what reactions may happen and what reaction products may be formed when some metallic or ceramic materials are placed under a chemical environment.

(2) When you want to know how to prepare materials.
The valence number of transition metal ions in the transition metal oxides depends on temperature and oxygen potential. In addition, when double oxides are formed with other oxides, this behavior depends also on these oxides. Chemical potential diagrams are quite useful to know under what conditions a particular compound can be formed.

(3) When you want to know the materials compatibilities.
There is some possibility that unexpected reactions may occur at interfaces between those materials which are used alone. when a chemical potential diagram is setup, all possible phase combinations are generated and checked. This is equivalent to checking all possible reactions. Therefore, look at such chemical potential diagrams leads to immediate understanding about what reactions may occur at interfaces between two materials.

The following facilities are required to run CHD
computers	NEC PC9801, DOS/V except for high resolution mode
display	640 x 400 dot excluding high resolution
plotter	Graphtec MIPLOT 3000, 4000
required memory size	640 kb
required software	MALT2

2-10-8 Yanagibashi, Taito-ku, Tokyo 111-0052 Japan Tel +81-3-5809-1132 Fax +81-3-5809-1138