David, You should know that within DFT calculations the zero of energy of a periodic system is NOT the vacuum. If you want to get the energy of vacuum you can simulate for example a surface with the "supercell" method ie including empty space between slabs. You will get the vacuum energy (and therefore also the work function) by plotting the potential far away from you slabs in the "empty" region. cyrille ================================================================== Cyrille Barreteau phone : +33 (0)1 69 08 29 51 CEA Saclay fax : +33 (0)1 69 08 84 46 IRAMIS, SPCSI, Batiment 462 email cyrille.barreteau at cea.fr 91191 Gif sur Yvette Cedex FRANCE ~~~~~~~~~~~~~~~~~~~~~~~~ Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ ==================================================================
________________________________ De: pw_forum-bounces at pwscf.org de la part de david grifith Date: sam. 23/10/2010 13:59 ?: PwSCF Forum Objet : [Pw_forum] positive fermi energy Dear All I get positive fermi energy (+7.8 eV) for bulk graphite by Quantum Espresso. Positive energy is meaningless for me here. Would you please say me that in whcih way QE selects the zero energy? As I know the vacuum should be considered as zero energy. I appreciate you in advance to solve the problem. -- Sincerely Yours David G. JCU -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/ms-tnef Size: 5742 bytes Desc: not available Url : http://www.democritos.it/pipermail/pw_forum/attachments/20101023/b353be7d/attachment.bin
