[Pw_forum] LDA+U in md calculations

[Han Hsu]

Jiayu and Matteo,

PRB volume 12 was published in 1975.

The paper discussing the contribution of dU/dV is actually:
Phys. Rev. B 79, 125124 (2009).

Regards,

Han

On Sun, April 4, 2010 10:36 pm, Matteo Cococcioni wrote:
>
> Dear Jiayu
>
> in order to fully account the effects of the +U correction on pressure
> one should include a contribution from dU/dV too.
> you may find this reference useful:
>
> Phys. Rev. B 12, 125124 (2009)
>
> regards,
>
> Matteo
>
>
> Jiayu Dai wrote:
>> Dear Matteo,
>>
>> Thanks for your comments. I am using the BOMD (pwscf). In my case, at
>> high density, i would expect the U should be different with the change
>> of ionic structures. In particular, i am concerning about the pressure.
>> I found a strange thing: the pressure with LDA+U is lower than the
>> pressure without U adding. As my experience, th pressure should be
>> larger when we added the U parameter, is it right?
>>
>> Besides, all the cases using LDA+U is about the transition metals, which
>> has the d or f electrons. How about the s or p electrons?
>>
>> Thanks.
>>
>> Jiayu
>>
>>
>>
>>
>> Dear Jiayu,
>>
>> are you talking about Car-Parrinello MD or Born-Oppenheimer MD (run with
>> pwscf)?
>> In any case lda+U MD is implemented in the sense that the code computes
>> the forces and the stress
>> as derivatives of  the lda+U energy functional. However it is not able
>> to account for the variation
>> of U with atomic position or with the cell. So it is a dynamics at fixed
>> U.
>> To account for this variation one would need to evaluate dU/dR or
>> dU/d\epsilon (R and \epsilon being atomic
>> positions and strains). Some work in this direction has been recently
>> done (not sure it's
>> published yet) by Kulik and Marzari.
>> If the structure you are interested in doesn't change dramatically
>> during the MD run I would expect
>> that keeping the same U is not too bad. but this is just my guess.
>>
>> regards,
>>
>> Matteo
>>
>>
>> Jiayu Dai wrote:
>>
>>> Dear developers,
>>>
>>> I have some doubts about the molecular dynamics calculations using
>>> LDA+U. First, is LDA+U performed in MD calculations? Because i did not
>>> find the Hubbard energy in the output file of MD. Second, i think the
>>> value of U be dependent on the temperature and density, also on the
>>> ionic structures. Therefore, since ionic positions are different in
>>> each time step, is U different at each time step? If so, the
>>> performance of LDA+U should be very difficult in MD.
>>>
>>> I did not know if what i said is right. Hope experts comment on this
>>> problem.
>>>
>>> Thanks a lot.
>>>
>>> Jiayu
>>> -------------------------------------------
>>> Jiayu Dai
>>> Department of Physics
>>> National University of Defense Technology,
>>> Changsha, 410073, P R China
>>> -----------------------------------------
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>>>
>>
>>
>>
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>
>
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> Matteo Cococcioni
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