[Pw_forum] Eigenfunctions in PWSCF

[Paolo Giannozzi]

On Jan 15, 2008, at 10:03 , Nicola Marzari wrote:

> These u_nk are what is stored in evc (I hope - I'm not that familiar
> with the innards of PWscf), in their *plane wave expansion*.

confirmed

> Note that if u_n0(r) has inversion symmetry, then the coefficients
> of the plane wave expansion are also real - albeit this has not been
> exploited, afaik, since early calculations (1991-1992) with the
> Cambridge CASTEP codes.

once upon a time there was a version of the PWscf code that exploited
inversion symmetry and used real wavefunctions and hamiltonian matrix
(at the time, the hamiltonian was still stored in a matrix). I think  
it was
also ported to separable pseudopotentials (i.e. hamiltonian stored as an
operator, not as a matrix). It disappeared a few years ago for no other
reason than the difficulty to keep 2N+1 versions of the code alive at  
the
same time.

It should be relatively straightforward to implement it again, though,
adapting the existing Gamma-only technology. It could be a good and
useful exercise for anybody who would like to learn how plane-wave
codes work

Paolo
---
Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222