[Pw_forum] question relating to crystal optimization

Giuseppe Mattioli giuseppe.mattioli at ism.cnr.it
Thu Apr 30 12:00:29 CEST 2015

Dear Neeraj Goel
When you optimize the parameters of a non-cubic lattice, you should prefer a vc-relax calculation. Otherwise, you must calculate the total energies on 
a two-dimension grid (at different a and c values, and centered "near" the expected minimum), and then you fit the minimum energy(a,c) with a given 
functional form or equation of state (paraboloid, ...).


On Thursday, April 30, 2015 10:34:46 AM Neeraj Goel wrote:
> i have optimized CuInS2, firstly by varying lattice parameter 'a' with
> respect to total energy and find the value of 'a' corresponding to the
> total minimum energy, keeping the lattice parameter 'c' constant.
> after that i have start varying lattice parameter 'c' and find  the
> value of 'c' corresponding to the total minimum energy, this time i
> have kept lattice parameter 'a' constant.
>           if i calculate in this manner than there will be many
> solutions of 'a' corresponding to the each value of 'c'. similar will
> be the case with 'c'.
>           so how will i justify the results as i have kept one
> parameter constant while varing the other?
>                                                                       regards
>                                                                   Neeraj Goel
>                                                                Indian
> School of Mines Dhanbad
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