<DIV>Thanks.<BR><BR><B><I>Stefaan Cottenier <Stefaan.Cottenier@fys.kuleuven.ac.be></I></B> wrote:
<BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">> According to the FAQ, when we calculate atomic energy within FLAPW, we<BR>should use only 1 k-point. I just can't understand this. I think if we<BR>calculate total bulk energy with 1000 k-points (for example), we should use<BR>identical k points for the calculation of atomic energy.<BR><BR>k-points for atoms are meaningless: they have no k-dispersion (=in a<BR>spaghetti plot, all band would be perfectly flat). That means that in a<BR>single k-point there is as much information as in 1000 k-points, and there<BR>is no need to take more than 1.<BR><BR>Another way to understand this: with bigger cells in real space, the<BR>reciprocal unit cell shrinks. Therefore, you can use less k-points for big<BR>cells, because they give you the same effective sampling of reciprocal space<BR>(the number of k-point per reciprocal volume should stay constant). Now, a<BR>free atom has a unit!
cell of
infinite volume, such that the reciprocal cell<BR>is infinitesimally small. Any number of k-points -- including just 1 -- will<BR>give you a perfect sampling for this 'reciprocal cell'.<BR><BR><BR>> The FAQ also told us for non-closed shell atoms, we should use<BR>spinpolarization. I wonder if the "closed shell atoms" is just confined to<BR>Inert atoms such as Ne, Ar etc?<BR><BR>No, it is relevant also for all atoms with closed subshells, such as Ca or<BR>Cd.<BR><BR>Stefaan<BR><BR>_______________________________________________<BR>Wien mailing list<BR>Wien@zeus.theochem.tuwien.ac.at<BR>http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien<BR></BLOCKQUOTE></DIV><p><br><hr size=1><b>Do You Yahoo!?</b><br>
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