[Wien] [second time query] sorry for my last email regarding "overestimated band gap by PBE" it was already answered by Prof. Xavier

[Dr. K. C. Bhamu]

Dear Prof. Xavier

I could not see your reply (it was in spam).

I got the point.

Thank you very much Prof. Xavier and Gavin

Cheers!!!


Bhamu


On Wed, Nov 23, 2016 at 4:15 AM, Dr. K. C. Bhamu <kcbhamu85 at gmail.com>
wrote:

> Dear Prof Peter,
>
> Please comment of my query when you get time:This is in the queue on my
> previous query regarding CH3NH3PbI3:
>
>>
>> I used two strategy and got different results:
>>
>>
>> The experimental band gap is 1.67 eV for orthorhombic lead halide
>> perovskite.
>>
>> I ran two cases (with PBE);
>> 1. with 1000 k, div: ( 11  7 11) and "min -j 'run_lapw -p -I -NI -i 120 *-ec
>> *0.00001 *-ec * 0.0001 -fc 1
>> 2. with 400 k, div: (  8  5  8)   and   min -j 'run_lapw -p -I -NI -i 120 *-ec
>> * 0.0001 *-ec * 0.0005 -fc 2'
>>
> -ec switch is used twice instead of ec and cc (it is by mistake)
> In case 2 with less k-points and normal scf criteria (-ec 0.0001 -ec
> 0.0005 -fc 2), I got minimized ENE than case 1. But the band gap is good
> from case 1.
>
>
> Results:
>
> 1. GAP 1.687 eV,    FER: 0.1030934295, ENE: -339059.11079128
> 2. GAP  1.777 eV,   FER: 0.1004906191, ENE: -339059.12432403
>
> You see that band gap is in the error of /+- 0.01eV.
>
>
>
>
> *[* next i tried with 1. with 1000 k, div: ( 11  7 11) and "min -j
> 'run_lapw -p -I -NI -i 120 -ec 0.00001 -cc 0.0001 -fc 1   >> second -ec is
> replaced by -cc 2. with 400 k, div: (  8  5  8)   and   min -j 'run_lapw -p
> -I -NI -i 120 -ec 0.0001 -cc 0.0005 -fc 2'      *
> *>> second -ec is replaced by -cc*
> *and nothing happened scf immediately got exit and the structure was
> already optimized]*
>
>>
>>
>> I did nothing special, just reduced rmt (5% and further rmt of "I" was
>> reduced by 0.02).
>> *Please correct me what is wrong here. Because usually PBE always
>> underestimates the experimental band gap.*
>>
>> Kind regards
>> Bhamu
>>
>
>
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