Added an input variable to SYSTEM namelist: tot_charge. The same information

could also be specified with a proper choise of nelec. The later option however
is more sensitive to human errors, especially when working on large systems
containing diverse elements (or when working in the middle of the night...) [silviu]


git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@2577 c92efa57-630b-4861-b058-cf58834340f0

CPV/input.f90

@@ -836,7 +836,7 @@ MODULE input
            etot_conv_thr, ekin_conv_thr, nspin, f_inp, nelup, neldw, nbnd,     &
            nelec, tprnks, ks_path, press, cell_damping, cell_dofree, tf_inp,   &
            refg, greash, grease, greasp, epol, efield, tcg, maxiter, etresh,   &
-           passop
+           passop, tot_charge
      !
      USE input_parameters, ONLY : wf_efield, wf_switch, sw_len, efx0, efy0,    &
                                   efz0, efx1, efy1, efz1, wfsd, wfdt, maxwfdt, &
@@ -1006,7 +1006,8 @@ MODULE input
      CALL ks_states_init( nspin, tprnks, tprnks_empty )
 
      CALL electrons_base_initval( zv, na_inp, ntyp, nelec, nelup, &
-                                  neldw, nbnd, nspin, occupations, f_inp )
+                                  neldw, nbnd, nspin, occupations, f_inp, &
+                                  tot_charge )
 
      CALL electrons_setup( empty_states_nbnd, emass, emass_cutoff, nkstot )
 

Doc/INPUT_CP

@@ -210,6 +210,10 @@ nelec          INTEGER
                number of electron in the unit cell. If not specified it is
                read from the pseudopotential
 
+tot_charge     INTEGER ( default = 0 )
+               total system charge. Used if nelec is not specified,
+               otherwise it is ignored.
+
 nbnd           INTEGER ( default = nelec / 2 )
                number of electronic states (bands) to be calculated.
 

Modules/electrons_base.f90

@@ -39,7 +39,7 @@
 
 
     SUBROUTINE electrons_base_initval( zv_ , na_ , nsp_ , nelec_ , nelup_ , neldw_ , nbnd_ , &
-               nspin_ , occupations_ , f_inp )
+               nspin_ , occupations_ , f_inp, tot_charge_ )
 
       USE constants, ONLY: eps8
       USE io_global, ONLY: stdout
@@ -51,7 +51,7 @@
       INTEGER, INTENT(IN) :: nbnd_ , nspin_
       CHARACTER(LEN=*), INTENT(IN) :: occupations_
       REAL(DP), INTENT(IN) :: f_inp(:,:)
-      REAL(DP) :: nelec, nelup, neldw, ocp, fsum
+      REAL(DP) :: nelec, nelup, neldw, ocp, fsum, tot_charge_
       INTEGER   :: iss, i, in
 
       nspin = nspin_
@@ -63,6 +63,7 @@
         DO i = 1, nsp_
           nelec = nelec + na_ ( i ) * zv_ ( i )
         END DO 
+        nelec = nelec - tot_charge_
       END IF
 
       IF( nelup_ > 0.0d0 .AND. neldw_ > 0.0d0 ) THEN

Modules/input_parameters.f90

@@ -337,6 +337,9 @@ MODULE input_parameters
           ! number of electrons, this parameter is MANDATORY in FPMD
           ! may be fractionary in PW, but not in CP and FPMD !
 
+        REAL(DP):: tot_charge = 0.0d0
+	  ! total system charge 
+
         REAL(DP) :: ecutwfc = 0.0d0
           ! energy cutoff for wave functions in k-space ( in Rydbergs )
           ! this parameter is MANDATORY in FPMD
@@ -552,7 +555,8 @@ MODULE input_parameters
 #endif
              noncolin, lspinorb, lambda, angle1, angle2, report, &
              constrained_magnetization, B_field, fixed_magnetization, &
-             sic, sic_epsilon, force_pairing, sic_alpha
+             sic, sic_epsilon, force_pairing, sic_alpha, &
+	     tot_charge
 
 
 !=----------------------------------------------------------------------------=!