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

[Giuseppe Mattioli]

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
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E-mail: <giuseppe.mattioli at ism.cnr.it>