From 5df79c53745fde5d6c3340a2979b1429cd5892c1 Mon Sep 17 00:00:00 2001 From: Henrik Rydberg Date: Sat, 8 Oct 2011 20:30:28 +0200 Subject: Initial import of htcd system 1.0 Signed-off-by: Henrik Rydberg --- src/labat/exchpt.f | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 src/labat/exchpt.f (limited to 'src/labat/exchpt.f') diff --git a/src/labat/exchpt.f b/src/labat/exchpt.f new file mode 100644 index 0000000..b44f49e --- /dev/null +++ b/src/labat/exchpt.f @@ -0,0 +1,33 @@ + subroutine exchpt(d,s,u,v,vx) +c gga91 exchange potential for a spin-unpolarized electronic system +c input d : density +c input s : abs(grad d)/(2*kf*d) +c input u : (grad d)*grad(abs(grad d))/(d**2 * (2*kf)**3) +c input v : (laplacian d)/(d*(2*kf)**2) +c output vx : exchange potential per electron + implicit double precision (a-h,o-z) + data a1,a2,a3,a4/0.19645d0,0.27430d0,0.15084d0,100.d0/ + data ax,a,b1/-0.7385588d0,7.7956d0,0.004d0/ + data thrd,thrd4/0.333333333333d0,1.33333333333d0/ + fac = ax*d**thrd + s2 = s*s + s3 = s2*s + s4 = s2*s2 + p0 = 1.d0/dsqrt(1.d0+a*a*s2) + p1 = dlog(a*s+1.d0/p0) + p2 = dexp(-a4*s2) + p3 = 1.d0/(1.d0+a1*s*p1+b1*s4) + p4 = 1.d0+a1*s*p1+(a2-a3*p2)*s2 + f = p3*p4 + p5 = b1*s2-(a2-a3*p2) + p6 = a1*s*(p1+a*s*p0) + p7 = 2.d0*(a2-a3*p2)+2.d0*a3*a4*s2*p2-4.d0*b1*s2*f + fs = p3*(p3*p5*p6+p7) + p8 = 2.d0*s*(b1-a3*a4*p2) + p9 = a1*p1+a*a1*s*p0*(3.d0-a*a*s2*p0*p0) + p10 = 4.d0*a3*a4*s*p2*(2.d0-a4*s2)-8.d0*b1*s*f-4.d0*b1*s3*fs + p11 = -p3*p3*(a1*p1+a*a1*s*p0+4.d0*b1*s3) + fss = p3*p3*(p5*p9+p6*p8)+2.d0*p3*p5*p6*p11+p3*p10+p7*p11 + vx = fac*(thrd4*f-(u-thrd4*s3)*fss-v*fs) + return + end -- cgit v1.2.3