Dear Dr. Li Chun, Can you drop me your tel to [EMAIL PROTECTED] I need your help. Rongqin
________________________________ From: Siesta, Self-Consistent DFT LCAO program, http://www.uam.es/siesta 代表 Chun Li Sent: 2007-3-19 (星期一) 16:00 To: SIESTA-L@listserv.uam.es Subject: [SIESTA-L] Posible SPAM: elastic constant calculations Dear SIESTA users, I used SIESTA to calculate the elastic constant C_33 of bulk ZnO. Both LDA and GGA are employed, respectively. But the obtained results are much larger than the experimental value (for LDA, I got 358 GPa; GGA, 282 GPa; but the experimental value is around 210 GPa). I wonder why such big error appears? What important factors might be responsible for that? Could anyone give me some ideas? In my calculations, first the cell is fully relaxed; after that I apply different strains in the c direction and evaluate their total energies, respectively. Then I fit the obtained energies to obtain the elastic constant. In both relaxation and energy calculations, double-zeta polarized numerical atomic orbitals basis sets for both Zn and O are used. Thank you and best regards, Chun Li
