[Wien] optimization for 225 (cubic) space group

[fatima DFT]

Thank you Dr. Tran

Yes, I took only 6x6x6 k-mesh for optimization.
I will test it further for 8x8x8, 10x10x10



On Fri, May 5, 2017 at 1:00 AM, <tran at theochem.tuwien.ac.at> wrote:

> Hi,
> If the SCF calculations were done with a value for a parameter (e.g.,
> RKmax, number of k-points or energy convergence criteria) that was
> not good enough, then this may introduce some noise such that the
> Murnaghan EOS can not fit perfectly the data and, therefore,
> leads to an optimised lattice parameter that depends on the chosen
> volumes to do the fit.
>
> In your case the fit does not seem perfect, but still reasonable
> since the variations in the lattice parameter are only at the
> third digit (at most tiny changes in the electronic properties).
>
> FT
>
> On Thursday 2017-05-04 20:34, fatima DFT wrote:
>
> Date: Thu, 4 May 2017 20:34:34
>> From: fatima DFT <fatimadft5 at gmail.com>
>> Reply-To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.
>> at>
>> To: A Mailing list for WIEN2k users <Wien at zeus.theochem.tuwien.ac.at>
>> Subject: [Wien] optimization for 225 (cubic) space group
>>
>> Dear All,I finished an optimisation for 225 space group with -15% to 25%
>> volume change.
>>
>> If I plot the optimization cure for different vol parameters, I see the
>> shape of ENE vs. Vol curve changes and the optimised lattice parametes also
>> changes (at
>> third digit).
>>
>> If I plot the curve for -15 to 25% then I get the below curve
>> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/1.ps
>>
>>
>> and the optimised lattice parameters are
>>
>> 21.1924 bohr =    11.2145 Ang
>>
>> For -10 to 25%,
>> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/2.ps
>>
>> 21.1984 bohr =    11.2177 Ang
>>
>> For -5 to 25%
>> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/3.ps
>>
>> 21.1915 bohr =    11.2140 Ang
>>
>> 0.0 to 25 %
>> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/4.ps
>>
>> 21.1917 bohr =    11.2141 Ang
>>  for 5.0  to 25 %
>> https://sites.google.com/site/dftfatima5/letter/mailing-list-queries/5.ps
>> 21.2026 bohr =    11.2199 Ang
>>
>>
>> My query is:
>>
>> 1. Why the optimised lattice parameters are changing if we select
>> different set of data points? The ground state should be same in all cases.
>> Is it?
>> 2.  We see from the lattice parameter the change is at third order, can
>> we take any lattice parameters (a0)? How much the third digit changes the
>> electronic
>> properties?
>>
>>
>> Warm regards
>> Fatima
>>
>>
>>
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