The definition of "alat" is arbitrary. Typically it is the lattice parameter, but it may be whatever. In vc-relax calculations alat is kept fixed to the starting value, IIRC, while basis vectors are updated.
P. On Fri, 2013-05-17 at 08:01 -0500, Dongsheng Zhang wrote: > Good morning everyone, > > > I tried to optimize a crystal structure by vc_relax, and found the > cell parameter kept changing until it is optimum. However, the value > of alat is always the same as the initial value. I think the alat > value should be linear with the cell parameter since the system is a > crystal. What is the relationship between alat and cell parameter? > Thank you for your help, > > > Dongsheng > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Paolo Giannozzi, Dept. Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
