Step 1: Prepare Files

Prepare the Thermodynamic Database file (.TDB)

In order to do the optimization, user must first define the model parameters to be optimized in the thermodynamic database (.tdb). The model parameters to be optimized can be defined in Pandat™ workspace where all the built-in keywords are automatically highlighted. It can also be done through outside text editor such as “Notepad”. Each model parameter that needs to be optimized is defined by the keyword “Optimization”. The format of defining a model parameter is:

Optimization [parameter name][low bound][initial value][high bound] N !

A definition sample for liquid phase in binary Al-Zn system is given as follows

$ Keyword Name Low Bound Init. Value High Bound

Optimization LIQ_AA 00; 60000 N !

Optimization LIQ_AAT -200; 20 N !

Optimization LIQ_BB -600000; 60000 N !

Optimization LIQ_BBT -200; 20 N !

Phase Liquid % 1 1 !

Constituent Liquid : Al, Zn : !

Optimization G(Liquid,Al;0) 298.15 G_Al_LIQUID; 6000 N !

Optimization G(Liquid,Zn;0) 298.15 G_Zn_LIQUID; 6000 N !

Optimization G(Liquid,Al,Zn;0) 298.15 LIQ_AA+LIQ_AAT*T; 6000 N !

Optimization G(Liquid,Al,Zn;1) 298.15 LIQ_BB+LIQ_BBT*T; 6000 N !

Two modes of optimization are allowed in the current version: one is “bounded” optimization and the other one is “no bound” optimization. Even though the low and high bounds will be in effect in the bounded optimization only, they are required for definition of model parameters in a TDB file. The model parameters can be named at user’ choices. It is suggested that the name is related to the phase to be optimized.

Prepare the Experimental File (.POP)

user need to provide their own experimental data file for optimization of model parameters. The most widely accepted format for experimental data file in the CALPHAD society is a POP file. PanOptimizer accepts most of the keywords in the POP format and adds a few special keywords. In a POP file, a phase can have four statuses: ENTERED, FIXED, DORMANT, and SUSPEND. The first two statuses were used most frequently. When phases are in the ENTERED status, PanOptimizer does not require user to input any initial values for calculation since the truly stable phase equilibria will be found automatically in this case with the built-in global optimization algorithm. On the other hand, for those phases in FIXED or DORMANT status, the initial values should be provided by the user. A detail description on keywords and syntax of a POP file recognized by PanOptimizer is given in Section Keywords and Syntax in POP File. Example POP files are provided in the installation dictionary of Pandat™.