# [Pw_forum] Problems with electrostatic corrections (Makov-Payne or density counter charge) for aperiodic systems in 4.2 version

ilyes hamdi iiysidi at gmail.com
Tue Apr 5 14:33:22 CEST 2011

Dear espresso users,

1) I'm a bit confused with the implementation of the Makov-Payne
electrostatic corrections in PW/makov-payne.f90 in Version 4.2:
- In their original paper, Makov and Payne define the first order correction
E11 =  - \alpha * q^2/(2\epsilon* L). This quantity should be negative for
cubic systems, however
the writing statement in PW/makov-payne.f90 subroutine defines the
correction to be -E11 (leading to a positive value).
- The second order correction E12 is propertional to q Q/L^3 and is also
defined as -E12 in the PW/makov-payne.f90 subroutine.
- The total energy should be Etot = E0 + E11 + E12 = E0 - \alpha *
q^2/(2\epsilon* L) + 2 \pi * q * Q / ( 3 \epsilon L^3), however it is
implemented as E0-E11-E12.

2) Why the DCC correction is disabled in version 4.2? Indeed when setting
asume_isolated = 'dcc' and &EE input parameters to their default  values, I
obtain an error message "DCC correction is disabled". Looking in the
PW/input.f90 subroutine, one found that the dcc correction is disabled by an
immediate call to errore subroutine.

Please can any one verify if I'm correct or did I miss something.

Best regards

--
Dr. Ilyes Hamdi, Assistant professor
Department of Electronic and Automatics,
Institute of Applied Sciences and Technology
Gafsa, Tunisia
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