Thanks for the helpful tutorial. But where is this Siesta pseudopotential database you mention on it?
Regards, Eric 2009/6/4 Zhong-Li Liu <zl.liu.c...@gmail.com> > Dear Andrei, > Thank you for your kind reply, and I shall have some tests > according your suggestion. > > Best regards, > > Zhongli > > On 04/06/2009, apost...@uni-osnabrueck.de <apost...@uni-osnabrueck.de> > wrote: > >> Dear Andrei, > >> You said in your SIESTA-tuto that the frozen phonon calculations > usually > >> proceed after CG relaxation. > > > > Dear Zhongli, > > this is not obligatory, techniclly speaking, but any book on phonons > > tells you how they are introduced from Taylor expansion arond > > the equilibrium. So, this equilibrium first has to be found. > > If your system does not have internal coordiates you don't have > > to worry (say, for pure NaCl you can calculate phonons right away > > for any lattice constant without a need to relax), but if the internal > > cordinates are present (as say in wurtzite or rutile) - yes, > > the relaxation in principle should be done first. > > Oterwise, you have a chance to get imaginary modes > > with eigenector pointing towards the relaxed > > geometry, where the system would be able to lower its energy. > > > >> Is that means we should > >> first set "MD.TypeOfRun CG" to relax > > > > yes > > > >> and then change it to "MD.TypeOfRun FC" > >> with "UseSaveData T" > > > > yes > > > >> and "MD. UseSaveXV T" to calculate the force constants? > > > > No, in fact I suggested to copy the relaxed coordinates > > into the .fdf file and then proceed phonons with > > MD. UseSaveXV F > > But it is just a suggestion. > > > > Best regards > > > > Andrei > > > > > -- > PhD. student of IAMP, Sichuan University, China > E-mail: zl.liu.c...@gmail.com > -- ========================================== Eric Perim Martins Universidade Estadual de Campinas - UNICAMP Instituto de Física Gleb Wataghin - IFGW Grupo de Sólidos Orgânicos e Novos Materiais - GSONM Departamento de Física Aplicada (DFA) - Sala 19 Campinas - São Paulo - Brasil CEP 13083-970 Telefone: (19)3521-0289 - Ramal 10289 MSN: pe...@nextwave.com.br ==========================================
