      FUNCTION VC (Q,A,RC,R)
C *** SEE R H LANDAU, PROGRAM LPOTT, 1981
C     THE COULOMP POTENTIAL IN MOMEMTUN SPACE FOR MOEMTN T.F. Q IN MEV,
C     R= CUTOFF RADIUS,    RC=COULOMB SPHERE RADIUS (ALL IN MEV-1)
C     N.B. DONT USE FERMIS
C     A= 3*Q1*Q2/(2 RC)
      IMPLICIT REAL*8 (A-H,K,M,O-Z)
      B = -A/(3*RC*RC)
      IF (Q.GT.1.) GO TO 10
C     SPECIAL Q=0 FORM --I THINK THIS IS OK
      RHL = 0.5/3.141593**2
      VC = RHL*(A*(RC**3)/3+B*(RC**5)/5+(RC*A/3)*(R*R-RC*RC))
      RETURN
 10   CONTINUE
      RHL = Q*RC
      S = SIN(RHL)
      C = COS(RHL)
      Q2 = Q*Q
      Q3 = Q2*Q
      Q5 = Q2*Q3
      RHL1 = 0.5/3.141593**2
      VC = RHL1*(A*(S-RHL*C)/Q3+B*((3*Q2*RC*RC-6)*S-(Q3*RC**3-6*RHL)*C)/
     1Q5+2*RC*A*(C-COS(Q*R))/(3*Q2))
      RETURN
      END
