On the contrary, overbinding should cause an overestimation of the l.c. A simplified explanation would be that LDA doesn't care about the gradients, only the local density value is taken into account, and stretching the atoms apart lowers that. Hence the overbinding - because unlike a solid, you can't stretch a single atom much and lower its energy in the same manner :)
2008/4/10, Marcel Mohr <[EMAIL PROTECTED]>: > > Hello everyone > > I am calculating CdSe. > Also I have a reasonable agreement from bulk modulus > (55.6 GPa (calc) vs. 53.8 (exp)), I find a slight overstimation of 1 % in > lattice constant. > > I know that LDA is often known to have an overbinding, that should result > in an underestimation of the lattice constant. > How serious should I take this overestimated lattice constant? > > Kind regards > Marcel > > ________________________________________________________________________ > Marcel Mohr Institut für Festkörperphysik, TU Berlin > marcel(at)physik.tu-berlin.de Sekr. EW 5-4 > TEL: +49-30-314 24442 Hardenbergstr. 36 > FAX: +49-30-314 27705 10623 Berlin > >
