How to run PARROT and create POP files

 Optimization module for evaluation of thermodynamic and kinetic model parameters  The objective of the PARROT module is to provide unified set of subroutines to be used in critical assessment of various thermochemical and kinetic parameters against avialble experimental and literature data  It makes use of the GES module to handle the models of the various phases  It makes use of POLY module to store and calculate complex heterogeneous equilibria What is PARROT?

Optimization method  The criteria for the best fit derived from the maximum of the likelyihood principle, will be minimum in the sum of squeare of residuals  Inaccuracies of experimental conditions can be taken in to account in two ways:  Independent state variables can be prescribed in the POLY interface. In this case equilibrium will be calculated with experimental values  The true value can be optimized by using one of the defined variables as the condition.

Commands available in the parrot AMEND_PARAMETER LIST_ALL_VARIABLES RESCALE_VARIABLES AMEND_SYMBOL LIST_CONDITIONS SAVE_PARROT_WORKSPACES BACK LIST_PARAMETERSET_ALTERNATE_MODE COMPILE_EXPERIMENTS LIST_PHASE_DATA SET_EXTERNAL_PARAMETER CONTINUE_OPTIMIZATION LIST_RESULT SET_FIX_VARIABLE CREATE_NEW_STORE_FILE LIST_STORE_FILE SET_INTERACTIVE EDIT_EXPERIMENTS LIST_SYMBOL_IN_GES SET_OPTIMIZING_CONDITION ENTER_PARAMETER MACRO_FILE_OPEN SET_OPTIMIZING_VARIABLE EXIT OPTIMIZE_VARIABLES SET_OUTPUT_LEVELS GOTO_MODULE READ_PARROT_WORKSPACES SET_SCALED_VARIABLE HELP RECOVER_VARIABLES SET_STORE_FILE INFORMATION REINITIATE

Creation of POP file single phase equilibria CREATE_NEW_EQUILIBRIUM 1,1 CHANGE_STATUS PHASE LIQUID=FIX 1 SET_CONDITION T=1379 P=1E5 X(LIQ,AU)= SET-REFERENCE-STATE AU LIQ * 1e5 SET-REFERENCE-STATTE CU LIQ * 1E5 EXPERIMENT HMR=1520:200

CREAT-NEW-EQUILIBRIUM 1 1 CHANGE-STATUS PHASE LIQUID FCC=FIX 1 SET-CONDITION X(FCC,CU)=0.14 P=1E5 EXPERIMENT T=970:2 $ H E Bennet, J inst of metals 1962 Creation of POP file single phase equilibria

$Congruent melting temperature of Fe2Nb: 1646 C [2011Vos] CREATE_NEW_EQUILIBRIUM 30,1 CHANGE_STATUS PHASE LIQUID,C14_LAVES=FIX 1 SET_CONDITION P=P0,X(LIQUID,NB)-X(C14_LAVES,NB)=0 SET_START_VALUE T= ,Y(LIQUID,NB)=0.33 EXPERIMENT T=1918:2 $ s-we 1 30 Creation of POP file Invariant reactions equilibria

E.G. 3 Phase equilbrium in binary system: CREAT-NEW-EQUILIBRIUM 1 1 CHANGE-STATUS PHASE FCC BCC LIQUID=FIX 1 SET-COND P=1E5 EXPERIMENT t=912:5

Creation of POP file Tables of experimental data $ Andersson 1988 CREATE_NEW_EQUILIBRIUM 128,1 CHANGE_STATUS PHASE FCC_A1, M7C3 M23C6=FIX 1 SET_CONDITION P=P0, T=1473 EXPERIMENT W(FCC,CR)=0.154:0.005 EXPERIMENT W(M7C3,CR)=0.629:0.05 EXPERIMENT W(M23C6,CR)=0.515:0.05

TABLE_HEAD 400 CREATE_NEW_EQUILIBRIUM CHANGE_STATUS PHASE BCC_A2, LIQ, FCC=FIX 1 SET_CONDITION P=P0, EXPERIMENT EXPERIMENT EXPERIMENT EXPERIMENT EXPERIMENT EXPERIMENT TABLE_VALUES $ T W(LIQ,C) W(LIQ,CR) W(BCC,C) W(BCC,CR) W(FCC,C) W(FCC,CR) TABLE_END $ set-weight Creation of POP file Tables of experimental data

System definition file: Set up file “TCM” file But how do we introduce functions and variables which should be optimized?

System definition file: Set up file “TCM” file

The PARROT module reserves 99 variables and can handle 1000 experimental measurements in one single assessment system

Some tricks Conflict in experimental data/ Experimental data which gives strange results More then one dependent experimental value exists for one independent experimental value Bo Jannson rule: If you have two conflicting datasets, then either one or the other may be correct or both are wrong. Both cannot be correct!

Some tricks  Use as few experiments as possible to obtain initial fit  Use weights!  It may be interesting to exclude from optimization intermediate phases at the initial stage and just optimize liquid and terminal phases. Metastable solubility lines should not contain strange kinks. The values for these phases can be later set fix in order to optimize parameters for intermediate phases  Take care about miscibility gaps  Phase with order/disorder require manual start values  In case terminal solutions are the same phase (e.g. Cr-Nb) pay attention that calculated equilibria are on the right side of the system.  A final optimization with all variables and all experimental values with appropriate weighing should be made!!!  Check continuously that optimized variables are within reasonable range of values. When variable starts to change several orders of magnitude during an optimization, one should reconsider weights and if too many parameters are used.

Thank you for your attention!