On Sat, September 12, 2009 08:15, udayagiri sai babu wrote: > Dear all > Can somebody clearly tell me how to define occupations from input. I cant > find much about that in this forum. The card "occupations" described in > the > example 11 for Al is not at all clear to me. What are those values mean. > Looking forward to your help....
It's quite easy, actually, there are only a couple of points you have to keep in mind: 1. if nspin=1 occupations can go from 0 to 2, you have to specify the occupation from the lower to the highest band and the sum of the occupations will have to be the number of electrons; 2. if nspin=2 occupations go from 0 to 1, you specify the occupation for spin up first, then for spin down (always on a newline); Let's say you want to reproduce the calculation of the Cr isolated atom, with semicore states in valence: 3s2 3p6 4s1 3d5 4p0 first with nspin=1 and spherical (as it is done in ld1.x): OCCUPATIONS 2 2 2 2 1 1 1 1 1 1 0 0 0 !3s2 3p6 4s1 3d5 4p0 then spin polarized (nspin=2), according to Hund's rule you have to maximize the total angular momentum: OCCUPATIONS 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 !3s2 3p6 4s1 3d5 4p0 Chrome is a lucky case, as it has a spherical ground state. As a last example let's take an oxygen atom (2s2 2p4) and set the occupations to reproduce the ld1.x calculation: OCCUPATIONS 2 4/3 4/3 4/3 or, equivalently: OCCUPATIONS 2 1.333333 1.333333 1.333334 I hope it helps, best regards -- Lorenzo Paulatto SISSA & DEMOCRITOS (Trieste) phone: +39 040 3787 511 skype: paulatz www: http://people.sissa.it/~paulatto/ ---------------------------------------------------------------- SISSA Webmail https://webmail.sissa.it/ Powered by SquirrelMail http://www.squirrelmail.org/
