SUBROUTINE GFREE0(ID)
C     =====================
C
C     depth-dependent quantities for the hydrogenic free-free Gaunt factor
C
      INCLUDE 'IMPLIC.FOR'
      INCLUDE 'BASICS.FOR'
      INCLUDE 'MODELQ.FOR'
      PARAMETER (THET0=5.0404D3,
     *           THET1=UN/THET0,
     *           A0=1.0823d0,
     *           B0=2.98D-2,
     *           C0=6.70D-3,
     *           D0=1.12D-2,
     *           A1=3.9999187d-3,
     *           B1=-7.8622889d-5,
     *           C1=1.070192d0,
     *           A2=6.4628601d-2,
     *           B2=-6.1953813d-4,
     *           C2=2.6061249d-1,
     *           A3=3.7542343d-2,
     *           B3=1.3983474d-5,
     *           C3=5.7917786d-1,
     *           A4=3.4169006d-1,
     *           B4=1.1852264d-2,
     *           XMIN=0.2D0,
     *           XMINI=UN/XMIN,
     *           THMIN=4.0D-2)
C
      T=TEMP(ID)
      THET=UN/MAX(THET0/T,THMIN)
      GF0(ID)=(A0+B0*THET)
      GF1(ID)=(A1+B1*THET)*THET+C1
      GF2(ID)=(A2+B2*THET)*THET+C2
      GF3(ID)=(A3+B3*THET)*THET+C3
      GF4(ID)=A4+B4*THET
      GF5(ID)=C0+D0*THET
      GF6(ID)=GF0(ID)+GF5(ID)*XMINI
C
C     auxiliary quantities for derivatives
C
      THT=THET0/T
      IF(THT.GE.THMIN) THEN 
         THET=THT
         GF0D(ID)=B0*THET1
         GF1D(ID)=(A1+B1*THET*TWO)*THET1
         GF2D(ID)=(A2+B2*THET*TWO)*THET1
         GF3D(ID)=(A3+B3*THET*TWO)*THET1
         GF4D(ID)=B4*THET1
         GF5D(ID)=D0*THET1
         GF6D(ID)=GF0D(ID)+GF5D(ID)*XMINI
       ELSE
         GF0D(ID)=0.
         GF1D(ID)=0.
         GF2D(ID)=0.
         GF3D(ID)=0.
         GF4D(ID)=0.
         GF5D(ID)=0.
         GF6D(ID)=0.
      END IF
      RETURN
      END