SUBROUTINE GFREED(ID,FR,CH,GFR,GFRD)
C     ====================================
C
C     Hydrogenic free-free Gaunt factor (GFR) and its derivative (GFRD)
C     for depth ID, frequency FR, and charge CH
C
      INCLUDE 'IMPLIC.FOR'
      INCLUDE 'BASICS.FOR'
      INCLUDE 'MODELQ.FOR'
      PARAMETER (C14=2.997925D14,
     *           XMIN=0.2D0,
     *           XMINI=UN/XMIN)
C
      X=C14*CH/FR
      IF(X.LT.UN) THEN
         GFR=((GF4(ID)*X-GF3(ID))*X+GF2(ID))*X+GF1(ID)
         GFRD=((GF4D(ID)*X-GF3D(ID))*X+GF2D(ID))*X+GF1D(ID)
       ELSE IF(X.LT.XMINI) THEN
         GFR=GF0(ID)+GF5(ID)*X
         GFRD=GF0D(ID)+GF5D(ID)*X
       ELSE
         GFR=GF6(ID)
         GFRD=GF6D(ID)
      END IF
      RETURN
      END