C   ************** SURFRHO.F ****************
C
C   CHARGE DENSITIES FOR SURFACE OF A SEMICONDUCTOR
C   VERSION 1.0 - WRITTEN BY R. M. FEENSTRA, JAN 2004
C
C   CONSTRUCT TABLE OF SURFACE CHARGE DENSITY VALUES
C
	SUBROUTINE SURFRHO(DELE,ESTART,NE,RHOS)
	DIMENSION RHOS(NE)
	DOUBLE PRECISION SUM
	COMMON/SURF/EN
C
	NEN=NINT((EN-ESTART)/DELE)+1
	RHOS(NEN)=0.
	SUM=0.
	DO 300 I=NEN+1,NE
         EF1=(I-1)*DELE+ESTART
         SUM=SUM+SIG(EF1,0.)
	   RHOS(I)=SUM*DELE
300   CONTINUE
	SUM=0.
	DO 310 I=NEN-1,1,-1
         EF1=(I-1)*DELE+ESTART
         SUM=SUM+SIG(EF1,0.)
	   RHOS(I)=SUM*DELE
310   CONTINUE
	RETURN
	END
C	
	FUNCTION SRHO(ENER,DELE)
	DOUBLE PRECISION SUM
	COMMON/SURF/EN
C
	SUM=0.
	E=EN
	IF (ENER.LT.EN) GO TO 200
100	E=E+DELE
	IF (E.GT.ENER) GO TO 900
	SUM=SUM+SIG(E,0.)*DELE
	GO TO 100
200	E=E-DELE
	IF (E.LT.ENER) GO TO 900
	SUM=SUM+SIG(E,0.)*DELE
	GO TO 200
900	SRHO=SUM
	RETURN
	END