[QE-users] Is it acceptable to neglect spin, magnetism and U for CPMD simulation of iron oxides (Fe2O3, Fe3O4 and FeO)

[Nicola Marzari]

Thanks Giuseppe,


couldn't agree more! Never being one to miss an opportunity to promote 
dft+hubbard, I would also add that these functional can be also more 
accurate, because they screen a fock-like term with awareness of the 
local bonding - see Iurii's just-out work on batteries:
https://arxiv.org/abs/2203.15732

			nicola

On 07/04/2022 12:39, Giuseppe Mattioli wrote:
> 
> Dear Kejiang
> 
> Only EXX functionals such as PBE0 or HSE significantly increase the 
> computation time. DFT+U has been primarily developed as a cost-effective 
> method to correct delocalization errors in the case of localized shells 
> such as those present in transition metal oxides. There are tons of 
> literature on this... In my opinion (and I've investigated several 
> similar system with the same purpose) you cannot neglect U, spin&co if 
> you want to obtain meaningful (i.e., publishable...) results. cp.x can 
> manage open shell systems with a fixed magnetic moment within the DFT+U 
> framework. But you must carefully setup and test your calculations, 
> which are a bit on the "nonstandard" side.
> HTH
> Giuseppe
> 
> Quoting likejiang at ustb.edu.cn:
> 
>> Dear QE-Users,
>>
>> I am planning to do some CPMD simulation about iron oxides (Fe2O3, 
>> Fe3O4 and
>> FeO) and their reactions with hydrogen at high temperature using cp.x 
>> of QE
>> 7.0.
>>
>> As it is well known that spin and magnetism are the most fundamental
>> characteristics for iron and its oxides, we should consider them (spin 
>> and
>> magnetism) and add U in many cases for 'scf' or 'relax'/'vc-relax'
>> calculations with pw.x.  But it seems that considering spin, magnetism 
>> and U
>> will make things more complicated and significantly increase the 
>> computation
>> time, I am wondering whether it is acceptable to neglect spin, 
>> magnetism and
>> U for CPMD simulation of iron oxides (Fe2O3, Fe3O4 and FeO) and their
>> reactions with Hydrogen gas. My goal is only to try to simulation the
>> reduction process in atomistic scale, and the CPMD trajectory results are
>> sufficient to capture the reduction mechanism while the accuracy of band
>> gap, magnetism is not the focus of my study.
>>
>> Any comments or suggestions will be much appreciated.
>>
>> Thanks,
>> Kejiang
>>
>> -------------------------------------------------
>> Dr. Kejiang Li
>> School of Metallurgical and Ecological Engineering,
>> University of Science and Technology Beijing
>> Xueyuan Rd., Haidian District, Beijing 100083, P. R. China
>> https://kejiangli.com/
> 
> 
> 
> GIUSEPPE MATTIOLI
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> Via Salaria Km 29,300 - C.P. 10
> I-00015 - Monterotondo Scalo (RM)
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> E-mail: <giuseppe.mattioli at ism.cnr.it>
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, SNSF
Head, Laboratory for Materials Simulations, Paul Scherrer Institut
Contact info and websites at http://theossrv1.epfl.ch/Main/Contact