C ETACFD    SOURCE    CHAT      05/01/12    23:45:46     5004           
c
             FUNCTION ETACONFUNCDER(VINT)
      IMPLICIT INTEGER(I-N)
      real*8    vint,etaconfuncder
      real*8    exm,qaa,pcc,eww,xk1,xk2,etb,exv,xep,paa,cco,
     .          exl,xnn,aaa,bbb
      common /MRScone/ exm,qaa,pcc,eww,xk1,xk2,etb,exv,xep,paa,cco,
     .                 exl,xnn,aaa,bbb
      if (exv.lt.0.D0) then
        etaconfuncder=0.D0
      else
        if (vint.lt.0.D0) then
          write(*,*)' ETACONDER var int',vint
          vint=0.D0
        endif
        etaconfuncder=-aaa*bbb*(vint+xk1)**(1.D0/exv)*dexp(-bbb*vint)
     .                -etb*xk2*vint/(xep+vint)**2
     .                +etb*xk2/(xep+vint)+aaa
     .                *(vint+xk1)**(1.D0/exv-1.D0)*dexp(-bbb*vint)/exv
        endif
      return
      end