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How to calculate MAE from DFT result in meV/f.u. unit?
Date: 2023/09/06 20:55
Name: Arifia Pratiwi N.   <arifia22jan@gmail.com>
References: https://www.openmx-square.org/openmx_man3.9/node114.html

Dear all,
I have calculated the MAE using the second variational method, but I am confused about the units. I think I can convert the units from Hartree (the result from SCF) to eV using 1 Hartree = 27.2114 eV, but it doesn't match the example result (in meV/f.u.).

The formula I used is MAE = (E_90 - E_0) / S, where S = a^2 for cubic lattice. The already example as mentioned in the OpenMX 3.9 manual is FePt cubic system with  lattice parameter a = 3.85 angstroms and MAE = 2.90 meV/f.u . There are four atoms (2 Fe and 2 Pt) in one lattice. Based on the formula, the MAE is 1.43553863e-05 Hartree = 3.90630158e-01 meV.

Is there anything missing in my unit conversion?

Regards
メンテ
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Re: How to calculate MAE from DFT result in meV/f.u. unit? ( No.1 )
Date: 2023/09/07 15:29
Name: T. Ozaki

Hi,

'f.u.' means the formula unit.
Since the unit cell contains two Fe and two Pt atoms,
we only have to divide the energy difference by 2.


Regards,

TO
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