Dear Meysam You cannot (easily) improve your calculation... Due to static correlation error, there is a strong interaction between the Zn 3d band and the O 2p band which push up the valence band maximum. It does not depend on the slab or bulk geometry. Your weapons could be some hybrid functional or a SIC scheme... HTH
Giuseppe On Friday 18 February 2011 12:12:10 meysam pazoki wrote: > Dear PWSCF users > In scf calculations of my 64 atom ZnO supercell(wich is relaxed by bfgs > method),the band gap of ZnO (1010) surface approximately disapear. > Espresso gives a 0.2 eV gap for this system in GGA functional.The surface > consist of 4 layers of ZnO bulk unit cell. > Is it due to surface states or not?how can i improve my calculations? > Thanks in advance > Best Regards > Meysam Pazoki > Ph.D student of physics > SUT -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** ? ?Giuseppe Mattioli ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?CNR - ISTITUTO DI STRUTTURA DELLA MATERIA ? ? ?v. Salaria Km 29,300 - C.P. 10 ? ? ? ? ? ? ? ? ? ?I 00015 - Monterotondo Stazione (RM) ? ? ? ? ? ? ?Tel + 39 06 90672836 - Fax +39 06 90672316 ? ? ? ?E-mail: <giuseppe.mattioli at ism.cnr.it>
