On Feb 18, 2010, at 6:46 AM, yukihiro_okuno at fujifilm.co.jp wrote: > > Dear PWSCF users.
Hi, Yiukihiro: > I want to calculate the band off set of semiconductor's hetero junction. > (semiconductor A/B junction) > In order to calculate the band offset value of valence band at the > interface, > I knew the average potential of electrostatic potential, must be > calculated > in the super cell calculation of A/B hetero junction. > (Baldereschi, et al Phys. Rev. Lett vol61 734 ) and the eigenvalue of > valence band top of semiconductors A and B, independently. > The band offset is defined by > > Band offset of valence band = (Ea-Eb)+(delta V), > > where Ea and Eb is the eigenvalue of the valence band top of the K.S.eq and > deltaV is > the difference of the average of the electrostatic potential of bulk like > region of > A and B semiconductor in the supercell. > > By the way, why the reference energy of the eigenvalue of the Kohn-Sham > equation > is the average of electro static potential ? because that average (which is ill-defined) is arbitrarily set to zero in PWscf (or at least it used to be so when the above mentioned paper was written). > Where in the formalism, the > K.S eq refers > the average of the electro static potential ? nowhere, explicitly. it is just the G=0 component of the potential. being ill-defined (as said), it is set to zero. *HENCE* the eigenvalues are referred to it (if you shift the average, the eigenvalues are all shifted accordingly). hope this is clear enough Stefano --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20100218/312065f4/attachment.htm
