Hi Pari, I think you should read this book.
Density functional theory: a practical introduction David S. Sholl,Janice A. Steckel http://books.google.com/books?id=Q8iNmtswLWYC&printsec=frontcover&dq=Janice+Steckel++Sholl&source=bl&ots=BBHL-SfWoi&sig=HLO4FmyafC7bKh22C0Qf1353Lug&hl=es&ei=KfaZTaajFImatwfQ95iVDA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBcQ6AEwAA#v=onepage&q&f=false 72/8 9.00000000000000000000 694/9 77.11111111111111111111 694/9-76.276 .83511111111111111111 So, where does the 7 Ry difference arise? Best regards Eduardo Menendez Departamento de Fisica Facultad de Ciencias Universidad de Chile Phone: (56)(2)9787439 URL: http://fisica.ciencias.uchile.cl/~emenendez > > > ---------- Mensaje reenviado ---------- > From: pari shok <parishok at gmail.com> > To: pw_forum at pwscf.org > Date: Mon, 4 Apr 2011 10:32:53 -0400 > Subject: [Pw_forum] Shift of Energy > Dear All, > Thank you very much for your help. > Please let me ask my final question w.r.t DOS shift of energy of SiC > supercell. > The total energy of the 8-atom cell of SiC is: -76.276 Ry, while that of > 72-atom SiC is -694 Ry. Neglecting almost -7 Ry, the total energy is scaling > accordingly. > However, I still see the shift of energy in DOS diagram of two slabs (the > max and min of bandgap shifts, although the gap is almost 2.1 eV for both > 4H-SiC slabs). I was wondering whether this shift of energy is inevitable or > it is as the result of my input file. > I kept k points (w.r.t. crystal), and cut off energy the same for both > structures. Should I scale the cut off energy as well. If positive, is there > any relation between scaling the cell and cut off energy. > As you know, I need to find a reference for my further calculations. > I really really appreciate your help. > Yours > P Shok > > > -- -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110404/67d0ffbe/attachment.htm