[Pw_forum] mean value point for arbitrary lattices

[Nicolas Chamel]

>The paper by Baldereschi on the mean value point [Phys. Rev. B 7, 5212
>- 5215 (1973)] is the "father" of all schemes on BZ integration based
>on "mean value" or "special" points.
>A generalization of Baldereschi's idea to more than just one point is
>given by Chadi and Cohen, Phys. Rev. B 8, 5747 - 5753 (1973).
>Monkhorst and Pack give a simpler (in my opinion) and more flexible
>generation scheme. For cubic lattices the two schemes lead to the same
>set of points.
>Accurate integration with just a few points is only possible when the
>system is highly symmetric.

Actually I'm using for my calculations the formulae of Hama et al (I gave the reference in an earlier message) which provide the coordinates and the weigths of an arbitrary number of special points. The code thus computes BZ integrals by  increasing the number of points until a given precision is reached. This guarantees that all quantities are computed with the same precision. This is however computationnaly very expensive and in some cases (computation of Fermi energies for instance) rather unnecessary. This is the reason why I'm also interested in the method of Baldereschi.

Nicolas Chamel.

Institut d'Astronomie et d'Astrophysique
Universite Libre de Bruxelles
CP 226
Boulevard du Triomphe
B-1050 Brussels
BELGIUM

tel. +32 2 650 35 72
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