[Wien] a note on lattice parameter optimization

[Dr. K. C. Bhamu]

No, I said the calculated gal is ~0.3eV less then the reported gap: HSE.


I tested this on more than 10 systems and in each case obsessed this band
gap discrepancy.

Regards
Bhamu

On Feb 8, 2018 3:05 PM, <tran at theochem.tuwien.ac.at> wrote:

> A band gap of 0.3 eV is very small and a change of lattice constant may
> be enough to close the band gap.
>
> On Thursday 2018-02-08 10:30, Dr. K. C. Bhamu wrote:
>
> Date: Thu, 8 Feb 2018 10:30:29
>> From: Dr. K. C. Bhamu <kcbhamu85 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: Re: [Wien] a note on lattice parameter optimization
>>
>> Yes, I used PBESol followed by mBJ.
>>
>> On Feb 8, 2018 2:28 PM, <tran at theochem.tuwien.ac.at> wrote:
>>      Hi,
>>
>>      Did you use mBJ to calculate the band gap in both procedures?
>>
>>      FT
>>
>>      On Thursday 2018-02-08 09:35, Dr. K. C. Bhamu wrote:
>>
>>            Date: Thu, 8 Feb 2018 09:35:08
>>            From: Dr. K. C. Bhamu <kcbhamu85 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] a note on lattice parameter optimization
>>
>>            Hello,
>>
>>            Using experimental lattice parameters(a Ang), I optimized the
>> structure with two options.
>>
>>            1. Directly optimized the structure without min_lapw ... and
>> the optimized lattice parameters are in the vicinity of Exp a (~0.01 Ang
>> accuracy) and the calculated band gap (from mBJ2) is in agreement with
>> reported value ~0.3 eV less.
>>
>>            2. First relaxed the structure and then optimized this relaxed
>> structure (without min_lapw ....). In this case the optimized lattice
>> parameters are reduced by ~0.05 Ang and the band gap vanished or largely
>> reduced.
>>
>>
>>            Why is the second way of doing band structure not working?
>>
>>            I tested it on many systems. In some case system became metal
>> and in some cases band gap largely reduced when  I used the fully relaxed
>> structure for optimization.
>>
>>
>>            Thanks,
>>
>>
>>            Bhamu
>>
>>
>>
>>
>>
>>
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>>
>>
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