How to create tdb files

Alan Dinsdale, Sandy Khvan“Thermochemistry of Materials” SRC

NUST, MISiS, Moscow, Russia

What are tdb files ?

• TDB files contain thermodynamic data necessary for calculating phase diagrams

• They can contain data for a single or multiple systems

• Generally they are used in conjunction with ThermoCalc although other software may be able to read them (with some restrictions)

General comments

• Always try to document your tdb files – Date– Author– Source of the data– Uncertainties about parameters or choice of

models• Remember that you may want to look at tdb

files you created 5 years ago, or someone else may want to use them

Resources

• ThermoCalc User Guide has a very comprehensive description

• Other tdb files• Unary.tdb has data for the elements

Structure

• The tdb format is very flexible – Can be very confusing and difficult to understand– ThermoCalc will assume missing parameters are zero– Length of lines limited to 80 characters

• Good practice:– Keep data for a phase or a system together– Do include parameters which have a zero value– Avoid default values for minimum and maximum

temperatures

$ Comments$ Use this area to indicate where the data come from

$ Elements used ELEMENT AG FCC_A1 1.0787E+02 5.7446E+03 4.2551E+01 !

$ Species if your data are expressed in non elemental entities SPECIES AL2O3 AL2O3 !

$ Phases – the number of sublattices PHASE HALITE % 2 1 1 !

$ Constituents – which elements or species are on which sublattices PHASE FCC_A1 ( 2 1 1 ! CONSTITUENT FCC_A1 : AG,CU,GE : C,VA : !

$ Functions – useful but not strictly necessaryFUNCTION GHSERGE 298.15 -9486.153+165.635573*T-29.5337682*T*LN(T)+5.568297E-3*T**2-1.513694E-6*T**3 +163298*T**(-1); 900 Y -5689.239+102.86087*T-19.8536239*T*LN(T)-3.672527E-3*T**2; 1211.4 Y -9548.204+156.708024*T-27.6144*T*LN(T)-859.809E26*T**(-9); 3200 N !

$ Data PARAMETER G(BCC_A2,FE:VA;0) 298.15 GHSERFE; 6000 N ! PARAMETER L(LIQUID,AG,MG;0) 298.15 -68930.725+0.684874*T; 3000 N !

Comments

• Comment lines begin with $• Use them !• Best to start non comment lines with a space

Elements

• Need to include these lines if you want to do mass based calculations

ELEMENT /- ELECTRON_GAS 0.0000E+00 0.0000E+00 0.0000E+00 ! ELEMENT VA VACUUM 0.0000E+00 0.0000E+00 0.0000E+00 ! ELEMENT AG FCC_A1 1.0787E+02 5.7446E+03 4.2551E+01 ! ELEMENT AL FCC_A1 2.6982E+01 4.5773E+03 2.8322E+01 ! ELEMENT AM DHCP 2.4306E+02 0.0000E+00 0.0000E+00 ! ELEMENT AS RHOMBOHEDRAL_A7 7.4922E+01 0.0000E+00 0.0000E+00 ! ELEMENT AU FCC_A1 1.9697E+02 6.0166E+03 4.7488E+01 ! ELEMENT B BETA_RHOMBO_B 1.0811E+01 1.2220E+03 5.9000E+00 !

Standard Element Reference Phase

Relative Atomic Mass (Atomic Weight)

H298-H0S298

• You can also copy the relevant lines from the unary database

Most statements are terminated with !

Species

• You need to identify SPECIES if your models involve non-elemental constitutents eg CaO, SiO2, O2, SO2, H2SPECIES AL2O3 AL2O3 !SPECIES Silica SI1O2 !SPECIES FE+2 FE/+2 !SPECIES SB-3 SB/-3 !

Species name Formula in terms of the defined elements. Note /+ and /- for charge

Phases

• These lines define which phases you want to use, describe the number of sublattices and how many sites there are on each sublattice

PHASE BCT_A5 % 1 1 !PHASE GAS % 1 1 !PHASE HALITE % 2 1 1 !PHASE SIGMA % 3 8 4 18 !

Phase name

Special set of characters

Number of sublattices

Number of sites on each sublattice

Type definition• Extra information about the phase– Magnetic information– Chemical ordering– Makes use of this special symbol in PHASE

definitionPHASE BCC_A2 B 2 1 3 ! PHASE FCC_A1 A 2 1 1 ! PHASE FCC_L12 AY 3 .75 .25 1 !

TYPE_DEF C GES AM_PH_DES @ COMP_SETS 2,,,,,,,, ! TYPE_DEF A GES AM_PH_DES @ MAGNETIC -3 0.280, ! TYPE_DEF Y GES AM_PH_DES FCC_L12 DISORD FCC_A1 ,,, !TYPE_DEF B GES AM_PH_DES @ MAGNETIC -1 0.400, !

Constituents

• Indicates which species go on which sublattices

PHASE FCC_A1 ( 2 1 1 !CONSTITUENT FCC_A1 : AG,CU,GE : C,VA : !

PHASE SIGMA % 3 8 4 18 ! CONSTITUENT SIGMA : AL,CO,FE : MO,TI: AL,CO,FE,MO,TI : !

Functions• Can be used to – refer to standard data eg for the elements GHSERFE,

GLIQGE

or– Data which you might want to manipulate

• The format is:

FUNCTION GHSERGE 298.15 -9486.153+165.635573*T-29.5337682*T*LN(T)+5.568297E-3*T**2-1.513694E-6*T**3 +163298*T**(-1); 900.00 Y -5689.239+102.86087*T-19.8536239*T*LN(T)-3.672527E-3*T**2; 1211.40 Y -9548.204+156.708024*T-27.6144*T*LN(T)-859.809E26*T**(-9); 3200.00 N !

Function name

Upper temperature limit, yes there is another range

Upper temperature limit, no more ranges

Lower temperature limit

; ends each range of data

• Syntax of data lines is very simple• Negative powers of T within brackets eg T**(-9)• LOG and LN are the same • Functions can call other functions

Parameters

• Similar to functions • Used for Gibbs energy (G), Interactions (G or L), Curie

temperature (TC) and the magnetic moment (BMAGN or BM)

FUNCTION GHSERFE 298.15 1225.7+124.134*T-23.5143*T*LN(T)-4.39752E-3*T**2-0.058927E-6*T**3 +77359*T**(-1); 1811 Y -25383.581+299.31255*T-46*T*LN(T)+2296.03E28*T**(-9); 6000.00 N ! PARAMETER G(BCC_A2,FE:VA;0) 298.15 GHSERFE; 6000 N ! PARAMETER TC(BCC_A2,FE:VA;0) 298.15 1043; 6000 N ! PARAMETER BM(BCC_A2,FE:VA;0) 298.15 2.22; 6000 N !

PARAMETER G(SIGMA,FE:CR:CR;0) 298.15 8*GFCCFE+22*GHSERCR+92300-95.96*T; 6000 N !

Interactions• Each line indicates a different term in the Redlich-Kister power series expression• The order of the parameter is given by the number after the semicolon ie. 0

refers to the regular solution parameter, 1 to the subregular term etc of the Redlich – Kister expression

• It is possible to miss lines out if the parameter is zero; however it is much clearer if you give the parameter explicitly

PARAMETER L(LIQUID,AG,MG;0) 298.15 -68930.725+0.684874*T; 3000 N !PARAMETER L(LIQUID,AG,MG;1) 298.15 16824.411-4.430152*T; 3000 N !PARAMETER L(LIQUID,AG,MG;2) 298.15 1928.379-1.977574*T; 3000 N !PARAMETER L(LIQUID,AG,MG;3) 298.15 -2624.584-2.440899*T; 3000 N !

Best if these are in alphabetical order

Phase with sublattices

• The parameter description used a colon to separate the sublattices– PARAMETER G(BCC_A2,FE:VA;0) 298.15 GHSERFE; 6000 N !– PARAMETER L(AL8MN5_D810,SI:MN:AL,MN;0) 298.15 0; 6000

N !