[CP2K-user] [CP2K:17252] Re: Anyone know about LibXC TB09 implementation?

[Nicholas Winner]

Here is my input file. I have changed 1 thing here, which is that I
manually adjusted the tb09 c parameter, which does open the gap. My working
theory is that TB09 in libxc does not solve self consistently, and must be
tuned like a +U or hybrid parameter.

On Wed, Jun 29, 2022 at 4:48 AM 'Frederick Stein' via cp2k <
cp2k at googlegroups.com> wrote:

> Dear Nick,
>
> I am not too familiar with that functional. If I understand the
> documentation of LibXC correctly, then your setup should be correct. In the
> literatur, people apparently use the same combination of functionals.
> Can you share your input file? With the scarce amount of information you
> provide, it is difficult to estimate what causes the deviation. It can be a
> too low cutoff, the wrong pseudo potential, the basis set etc.
>
> Best,
> Frederick
>
> nwi... at berkeley.edu schrieb am Dienstag, 28. Juni 2022 um 22:26:29 UTC+2:
>
>> Does anybody happen to know how to properly use the LIBXC implementation
>> of the TB09 meta GGA exchange functional? I've applied it to GaAs with
>> tight k-point sampling and the resultant DOS still has a band gap of ~0.7
>> eV when the literature shows TB09 should give ~1.5eV
>>
>> I've accessed it using
>>
>> &XC_FUNCTIONAL
>>   &MGGA_X_TB09
>>   &END
>>   &LDA_C_PW
>>   &END
>> &END
>>
>> The TB09 MGGA has a self consistent solution for the parameter "c" in the
>> original implementation, is that not being done here?
>>
>> Not too familiar with how libxc works under the hood but maybe someone
>> else does.
>>
>> -Nick
>>
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