[QE-developers] Madelung constant values in Makov-Payne correction

[Pietro Delugas]

Hello 

It is because one can adopt  different definitions of the length parameter L, the cubic root of the cell volume, the length of the lattice vectors, the side of the corresponding cubic cell.
 
Pietro 

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From: Jacob Williams
Sent: Friday, July 17, 2020 3:52 PM
To: developers at lists.quantum-espresso.org
Subject: [QE-developers] Madelung constant values in Makov-Payne correction

Dear all,

The work of Lento et al. at https://doi.org/10.1088/0953-8984/14/10/314 gives the Madelung constants for (simple cubic, bcc, fcc) as (2.8373, 2.8883, 2.885) respectively; these values are used in makov_payne.f90 for at least QE 6.3 and 6.5 (which, of course, references the above paper).

However, some other works that give Madelung constants in the context of the Makov-Payne correction have the values (2.8373, 3.6392, 4.5848) for the same lattices. For instance, Leslie and Gillam’s 1985 paper (cited in the Makov-Payne reference) https://doi.org/10.1088/0022-3719/18/5/005, and the paper of Dabo et al. at https://doi.org/10.1103/PhysRevB.77.115139 use these larger values for bcc and fcc.

Could you tell me the cause of this distinction?

Sincerely yours, 

Jacob Williams
PhD Student, Yang group
Duke University Dept. of Chemistry

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