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_A E E E+01 ! $ Species if your data are expressed in non elemental entities SPECIES AL2O3 AL2O3 ! $ Phases – the number of sublattices PHASE HALITE % ! $ Constituents – which elements or species are on which sublattices PHASE FCC_A1 ( ! CONSTITUENT FCC_A1 : AG,CU,GE : C,VA : ! $ Functions – useful but not strictly necessary FUNCTION GHSERGE *T *T*LN(T) E-3*T** E-6*T** *T**(-1); 900 Y *T *T*LN(T) E-3*T**2; Y *T *T*LN(T) E26*T**(-9); 3200 N ! $ Data PARAMETER G(BCC_A2,FE:VA;0) GHSERFE; 6000 N ! PARAMETER L(LIQUID,AG,MG;0) *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 E E E+00 ! ELEMENT VA VACUUM E E E+00 ! ELEMENT AG FCC_A E E E+01 ! ELEMENT AL FCC_A E E E+01 ! ELEMENT AM DHCP E E E+00 ! ELEMENT AS RHOMBOHEDRAL_A E E E+00 ! ELEMENT AU FCC_A E E E+01 ! ELEMENT B BETA_RHOMBO_B E E E+00 ! Standard Element Reference Phase Relative Atomic Mass (Atomic Weight) H 298 -H 0 S 298 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, H2 SPECIES AL2O3 AL2O3 ! SPECIES Silica SI1O2 ! SPECIES FE+2 FE/+2 ! SPECIES SB-3 SB/-3 ! Species nameFormula 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 % ! PHASE SIGMA % ! 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 definition PHASE BCC_A2 B ! PHASE FCC_A1 A ! PHASE FCC_L12 AY ! TYPE_DEF C GES COMP_SETS 2,,,,,,,, ! TYPE_DEF A GES MAGNETIC , ! TYPE_DEF Y GES AM_PH_DES FCC_L12 DISORD FCC_A1,,, ! TYPE_DEF B GES MAGNETIC , !

Constituents Indicates which species go on which sublattices PHASE FCC_A1 ( ! CONSTITUENT FCC_A1 : AG,CU,GE : C,VA : ! PHASE SIGMA % ! 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 *T *T*LN(T) E-3*T** E-6*T** *T**(-1); Y *T *T*LN(T) E-3*T**2; Y *T *T*LN(T) E26*T**(-9); 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 *T *T*LN(T) E-3*T** E-6*T** *T**(-1); 1811 Y *T-46*T*LN(T) E28*T**(-9); N ! PARAMETER G(BCC_A2,FE:VA;0) GHSERFE; 6000 N ! PARAMETER TC(BCC_A2,FE:VA;0) ; 6000 N ! PARAMETER BM(BCC_A2,FE:VA;0) ; 6000 N ! PARAMETER G(SIGMA,FE:CR:CR;0) *GFCCFE+22*GHSERCR *T; 6000 N !

Interactions PARAMETER L(LIQUID,AG,MG;0) *T; 3000 N ! PARAMETER L(LIQUID,AG,MG;1) *T; 3000 N ! PARAMETER L(LIQUID,AG,MG;2) *T; 3000 N ! PARAMETER L(LIQUID,AG,MG;3) *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) GHSERFE; 6000 N ! – PARAMETER L(AL8MN5_D810,SI:MN:AL,MN;0) ; 6000 N !