On Saturday 31 December 2005 06:11, W. YU wrote: > 2. I did some calculations on alkali hydrides such as > LiH and NaH. For LiH, the LDA using Von Barth and Car > scheme give a much smaller lattice constant
I am not sure what PP was used in this paper: G. Roma et al, Solid State Commun. 98, p.203 (1996), but it might well be the same that one finds on www.pwscf.org. They get -5.1% for the lattice constant, -2.5% taking into account finite temperature and zero-point effects. Is this what you get? it is nothing to write home about, but it is a decent result. GGA should yield a larger lattice parameter. > For NaH system, the VBC LDA gives a lattice constant very > close to the experimental one and the GGA gives larger lattice > constant. nothing surprising here > When the vibrating effect [...] is taken into account, the resulting > lattice constant is much larger than the experiment. I don't expect finite-temperature and zero-point effects to be larger in NaH than in LiH, so with LDA you will get something in the order of +2% for the lattice constant. It is not very good but it isn't very bad either Paolo -- Paolo Giannozzi e-mail: giannozz at nest.sns.it Scuola Normale Superiore Phone: +39/050-509876, Fax:-563513 Piazza dei Cavalieri 7 I-56126 Pisa, Italy
