helect.f

      FUNCTION HELECT(N,P,H,F)
      IMPLICIT DOUBLE PRECISION (A-H,O-Z)
      DIMENSION P(*), H(*), F(*)
C***********************************************************************
C
C    SUBROUTINE CALCULATES THE ELECTRONIC ENERGY OF THE SYSTEM IN EV.
C
C    ON ENTRY N = NUMBER OF ATOMIC ORBITALS.
C             P = DENSITY MATRIX, PACKED, LOWER TRIANGLE.
C             H = ONE-ELECTRON MATRIX, PACKED, LOWER TRIANGLE.
C             F = TWO-ELECTRON MATRIX, PACKED, LOWER TRIANGLE.
C    ON EXIT
C        HELECT = ELECTRONIC ENERGY.
C
C    NO ARGUMENTS ARE CHANGED.
C
C***********************************************************************
      ED=0.0D00
      EE=0.0D00
      K=0
      NN=N+1
      DO 20 I=2,NN
         K=K+1
         JJ=I-1
         ED=ED+P(K)*(H(K)+F(K))
         IF (I.EQ.NN) GO TO 20
         DO 10 J=1,JJ
            K=K+1
   10    EE=EE+P(K)*(H(K)+F(K))
   20 CONTINUE
      EE=EE+.5D00*ED
      HELECT=EE
      RETURN
C
      END