[CPMD-list] on RAGGIO and KPOINTS units

[Axel Kohlmeyer]

>>> "EM" == Eduardo Ariel Menendez P <Eduardo> writes:

EM> Hello everybody,

hello eduardo,


EM> Just two silly questions,

EM> 1. What is the meaning of
EM> "the width of the ionic charge distribution" [i.e. the keyword RAGGIO]?

to quote from ener.inc:

C     == ION-ION INTERACTION:                                         ==
C     == The ion-ion interaction energy, the Hartree and the local    ==
C     == pseudo potential energy are diverging due to the presence of ==
C     == slowly decaying Coulomb forces                               ==
C     == To calculate ion-ion interaction, we replace ionic point     ==
C     == charges by Gaussian charge distributions determined by raggio==
C     == (in RHOPS in G space)                                        ==
C     == E_{Ion-Ion} = Hartree term due to RHOPS -ESELF - ESR         ==
C     == ESELF: Self-energy (Sum_i Zv(i)^2 /Raggio(i) )               ==
C     ==        calculated in RINFORCE once                           ==
C     == ESR:   Residual part of the ion-ion interaction              ==
C     ==        (nearest neighbor energy)                             ==



EM> 2. What are the units of the KPOINTS when they are given in cartesian
EM> coordinates. The manual says "units 1/a". What is "a" for a non cubic
EM> lattice? Is there any option to give the KPOINTS in units of 2pi/a  ?

a is the lattice constant in atomic units. there may be an error
in the manual, since the following two statements in the &SYSTEM section
are equivalent (for a system with a simple cubic cell):

KPOINTS MONKHORST-PACK FULL
 2 2 2

and

KPOINTS
 4
     0.25000      0.25000      0.25000    0.25000
     0.25000      0.25000     -0.25000    0.25000
     0.25000     -0.25000      0.25000    0.25000
     0.25000     -0.25000     -0.25000    0.25000

please check out the SUPERCELL section of the cpmd output.

regards,
        axel kohlmeyer.



EM> Thank you,

EM> Eduardo A. Menendez Proupin
EM> Department of Physics
EM> Faculty of Science
EM> University of Chile
EM> Las Palmeras 3425
EM> Ñuñoa, Santiago
EM> Chile
EM> Phone: 56+2+678 74 11
EM> http://fisica.ciencias.uchile.cl/~emenendez/

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EM> http://cpmd.org/mailman/listinfo/cpmd-list



--

=======================================================================
Axel Kohlmeyer       e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.