Line data    Source code

       1             : MODULE m_pbecor2
       2             : !---------------------
       3             : ! slimmed down version of gcor used in pw91 routines, to interpolate
       4             : ! lsd correlation energy, as given by (10) of
       5             : ! j. p. perdew and y. wang, phys. rev. b {\bf 45}, 13244 (1992).
       6             : ! k. burke, may 11, 1996.
       7             : !---------------------
       8             : CONTAINS
       9   446238159 :    SUBROUTINE pbecor2( &
      10             :       a,a1,b1,b2,b3,b4,rtrs, &
      11             :       gg,ggrs)
      12             :       IMPLICIT NONE
      13             : 
      14             :       REAL, INTENT (IN)  :: a,a1,b1,b2,b3,b4,rtrs
      15             :       REAL, INTENT (OUT) :: gg,ggrs
      16             : 
      17             :       REAL :: q0,q1,q2,q3
      18             : !     ..
      19   446238159 :       q0 = -2.e0*a* (1.e0+a1*rtrs*rtrs)
      20   446238159 :       q1 = 2.e0*a*rtrs* (b1+rtrs* (b2+rtrs* (b3+b4*rtrs)))
      21   446238159 :       q2 = log(1.e0+1.e0/q1)
      22   446238159 :       gg = q0*q2
      23   446238159 :       q3 = a* (b1/rtrs+2.e0*b2+rtrs* (3.e0*b3+4.e0*b4*rtrs))
      24   446238159 :       ggrs = -2.e0*a*a1*q2 - q0*q3/ (q1* (1.e0+q1))
      25             : 
      26   446238159 :    END SUBROUTINE pbecor2
      27             : END MODULE m_pbecor2