[QE-users] gamma_gamma

[Aleksandra Oranskaia]

Dear QE users and developers,

I would be very grateful if someone were kind to help me with very basics
about the oxygen atom and its 6 valence electrons (pbe pseudopotential).

Doing SCF with gamma
and occupations = 'from_input' (1. 1. 1. 1. 0. 0. 0. 0. | 1. 1. 0. 0. 0. 0.
0. 0.) I got total energy -32.69566577 Ry,
and occupations = 'smearing' (that in output were printed as: 1. 1. 1. 1.
0. 0. 0. 0. | 1. 1/3 1/3 1/3 0. 0. 0. 0.) i got total energy -32.66588752
Ry.
With all-electron numerical orbital FHI-aims I obtained the same picture
with 400meV difference in favor of the 1st case.
Question1: Is that a physical result? Should not be the 2nd case lower in
energy?

Doing SCF with 1 1 1 'k-grid'
and occupations = 'from_input' (1. 1. 1. 1. 0. 0. 0. 0. | 1. 1. 0. 0. 0. 0.
0. 0.) I got total energy -32.66511579 Ry,
and occupations = 'smearing' (that in output were printed as: 1. 1. 1. 1.
0. 0. 0. 0. | 1. 1/3 1/3 1/3 0. 0. 0. 0.) i got total energy -32.66588710
Ry.
Question2: Why do the results differ from gamma treatment?

Question3: Why was it possible to converge (1. 1. 1. 1. 0. 0. 0. 0. | 1. 1.
0. 0. 0. 0. 0. 0.) and not possible to converge the same systems with (1.
1. 1. 1. 0. 0. 0. 0. | 1. 0. 1. 0. 0. 0. 0. 0.) or (1. 1. 1. 1. 0. 0. 0. 0.
| 1. 0. 0. 1. 0. 0. 0. 0.)?

Sorry for shallow questions,
Hope to hear from you,
Al.
---
Best wishes,
Alex (she/her/hers),
phd candidate in chemical sciences
'I.. a universe of atoms, an atom in the universe' (Richard P. Feynman)
https://cpms.kaust.edu.sa/

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