[Pw_forum] question pertaining to subroutine regterg

[willy kohn]

Hi, there:

I was stucked again in the subroutine regterg in the file regterg.f90 when I
read the pwscf code. There are two things bothering me.

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. For example, in the line 136,


 CALL DGEMM( 'T', 'N', nbase, nbase, ndim2, 2.D0 , &
               psi, ndmx2, hpsi, ndmx2, 0.D0, hr, nvecx )

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? Can the matrix hr be a Hermitian one?


Best,

Wei
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