[Wien] Ni-non magnetic problem with GGA

[Andrei Postnikov]

Hallo Dominik,

Some discontinuity might occur as the number of vectors
in the G-summation experiences jumps at some volumes,
as you keep GMAX fixed, but vary the volume -
and hence reciprocal lattice constant.
The effect must decrease as you take larger GMAX.
How large - depends.
GMAX=12 is anyway too small for a reliable GGA calculation.
Fine G-mesh is less essential for LDA, that's why
you don't see problems there.

Good luck,

Andrei Postnikov

 +-- Dr. habil. Andrei Postnikov ----- Tel. +49-541-969.2377 -- Fax .2351 ---+
 | Universitaet Osnabrueck - Fachbereich Physik, D-49069 Osnabrueck, Germany |
 +-- apostnik at uos.de --------- http://www.home.uni-osnabrueck.de/apostnik/ --+

On Tue, 26 Oct 2004, Dominik Legut wrote:

| Dear Wien users,
|
| We have found some incosistency during energy-volume calculation of Ni
| with GGA. When we ran a calculation of the bcc or fcc structure of Ni
| without spin-polarization (NM) the energy-volume curve is  not
| continuous (the energy jump is about 5mRy/atom).
| The situation occurs at certain volumes, that are depending on the Rkmax
| parameter. For instance, for the Rkmax=9.5 the discontinuity of total
| energy for energy-volume of bcc non-magnetic Ni is about 66.2 a.u.^3/atom, i.e.
| 90% of equilibrium volume per atom. In close neighbourhood of the
| discontiunity the calculations do not converge. It does not depend on the
| number of K-points. We have checked it for a few calculations within
| (290-637)KPs in ireduccible Brill. zone.
|
| The discontinuity vanishes if the spin-polarization is turned on for
| GGA or the LDA(LSDA) is used.
|
| Has anyone experienced such a strange behavior ?
| Please, comment it.
|
| Parameteres of the calculation:
| RMT=2.0
| GMAX=12
| lmax=9
| KPs input: 2000-4000
| Rkmax=6-10
|
| Thank a lots
|
| M. Zeleny, D. Legut
|