[Pw_forum] About phonon calculation and IR

[Paolo Giannozzi]

On Monday 11 July 2005 10:09, Diep Vinh Quang wrote:

> 1. Why the program phcg.x cannot use with ultra-solf pseudopotentials ?

because it takes time to implement US-PP and nobody ever did it

> what is the different between phcg.x and ph.x

the former uses a "global minimization" approach: the linear response
functions dpsi/du, where u is the atomic displacement from equilibrium
(or dpsi/dE in the case of an electric field) are calculated from the
minimisation of a quadratic functional, that is, the solution of a linear
system involving all dpsi/du . See for instance Rev. Mod. Phys. 73, 515
(2001), Sec. II C

Paolo

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Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
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