C INVARQ    SOURCE    CHAT      05/01/13    00:42:24     5004           

      SUBROUTINE INVARI_Q (SIG,N,Q)
      IMPLICIT INTEGER(I-N)
      integer n
      real*8 sig(n),q,J2
      call Invari_J2(sig,n,J2)
      if (j2.le.0.D0) then 
        q=1.D-17
        return
      endif
      q=dsqrt(3.D0*J2)
      return
      end