[Pw_forum] Making density matrix in sum_band subroutine

[Min Seung Kyu]

Dear users and developers,

I'm studying PWSCF source code.

Looking in 'sum_band_gamma' subroutine in 'sum_band.f90', this subroutine 
does two FFTs at the same time.

DO ibnd = 1, nbnd, 2
    psic(:) = ( 0.D0, 0.D0 )
    IF ( ibnd < nbnd ) THEN
       !
       ! ... two ffts at the same time
       !
       psic(nls(igk(1:npw)))  = evc(1:npw,ibnd) + &
                                   ( 0.D0, 1.D0 ) * evc(1:npw,ibnd+1)
       psic(nlsm(igk(1:npw))) = CONJG( evc(1:npw,ibnd) - &
                                   ( 0.D0, 1.D0 ) * evc(1:npw,ibnd+1) )
    ELSE
       psic(nls(igk(1:npw)))  = evc(1:npw,ibnd)
       psic(nlsm(igk(1:npw))) = CONJG( evc(1:npw,ibnd) )
    END IF
    CALL cft3s( psic, nr1s, nr2s, nr3s, nrx1s, nrx2s, nrx3s, 2 )
    w1 = wg(ibnd,ik) / omega
    !
    ! ... increment the charge density ...
    !
    IF ( ibnd < nbnd ) THEN
       !
       ! ... two ffts at the same time
       !
       w2 = wg(ibnd+1,ik) / omega
    ELSE
       w2 = w1
    END IF
    DO ir = 1, nrxxs
       rho(ir,current_spin) = rho(ir,current_spin) + &
                              w1 *  DBLE( psic(ir) )**2 + &
                              w2 * AIMAG( psic(ir) )**2
    END DO
ENDDO

I changed above lines into below.

DO ibnd = 1, nbnd
    psic(:) = ( 0.D0, 0.D0 )
    psic(nls(igk(1:npw)))  = evc(1:npw,ibnd)
    CALL cft3s( psic, nr1s, nr2s, nr3s, nrx1s, nrx2s, nrx3s, 2 )
    w1 = wg(ibnd,ik) / omega
    !
    ! ... increment the charge density ...
    !
    DO ir = 1, nrxxs
       rho(ir,current_spin) = rho(ir,current_spin) + &
                              w1 * ( DBLE( psic(ir) )**2 + &
                                    AIMAG( psic(ir) )**2 )
    END DO
END DO

But I failed to reproduce charge densities.

For 'co.rx.in' in example03 folder, I got this message.

WARNING: integrated charge=     6.86602003, expected=    10.00000000

Could you tell me what is wrong?

Thank you in advance.

Sincerely, Min.


-------------------------------Sig.---------------------------
Center for Superfunctional Materials, Department of Chemistry,
Pohang University of Science and Technology (POSTECH)

Mr. Seung Kyu, Min

Ph.D. Candidate

E-Mail: min0220 at postech.ac.kr
Tel.  : 82-54-279-5858
----------------------------------------------