how to create tdb files alan dinsdale, sandy khvan “thermochemistry of materials” src nust,...
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![Page 1: How to create tdb files Alan Dinsdale, Sandy Khvan “Thermochemistry of Materials” SRC NUST, MISiS, Moscow, Russia](https://reader035.vdocument.in/reader035/viewer/2022081421/56649e9f5503460f94ba1eb5/html5/thumbnails/1.jpg)
How to create tdb files
Alan Dinsdale, Sandy Khvan“Thermochemistry of Materials” SRC
NUST, MISiS, Moscow, Russia
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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)
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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
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Resources
• ThermoCalc User Guide has a very comprehensive description
• Other tdb files• Unary.tdb has data for the elements
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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
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$ 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 !
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Comments
• Comment lines begin with $• Use them !• Best to start non comment lines with a space
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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 !
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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
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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
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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, !
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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 : !
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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
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• 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
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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 !
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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
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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 !