[Pw_forum] question pertaining to subroutine regterg

[Paolo Giannozzi]

On Apr 2, 2008, at 22:43 , willy kohn wrote:

> One is in the subroutine, the variables psi and hpsi are declared  
> as complex(dp),
> however, they are used as parameters to call the  Lapack subroutine  
> DGEMM,
> which requires real numbers.

a vector of N complex numbers is equivalent to a vector of 2N real  
numbers

> The other one is about the diagonalization of the reduced  
> hamiltonian hr, which is
> declared as a real symmetric matrix in the subroutine. But in  
> general, the
> wavefunction psi is complex, how can we guarentee all the elements  
> in the matrix
> is real?

at k=0 the wavefunctions are real in real space, so the hamiltonian  
is also real

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