1 files changed, 26 insertions, 0 deletions

diff --git a/src/labat/grad.f b/src/labat/grad.f
new file mode 100644
index 0000000..845ed5a
--- /dev/null
+++ b/src/labat/grad.f
@@ -0,0 +1,26 @@
+      subroutine grad(r,db,i,imin,imax,done,gradd,gradup,graddn)
+c  grad calculates the derivative of db with respect to r, at
+c  position r(i).
+c  input r              : radial coordinate (array)
+c  input db             : spin-up and down densities (array)
+c  input i              : counter, i.e. current position = r(i)
+c  input imin           : min value of i
+c  input imax           : max value of i
+c  in/output done       : true if density is splined
+c  output gradd         : grad(density)
+c  output gradup,graddn : grad(density), spin up and down
+      implicit logical (a-z)
+      logical done
+      double precision r,db,gradd,gradup,graddn,db2,deriv
+      integer i,imin,imax
+      dimension r(561),db(2,561),db2(2,561)
+      common/ggagra/db2
+      if (.not.done) then
+         call spline(r,imin+1,imax,db,db2)
+         done = .true.
+      endif 
+      gradup = deriv(r,db,db2,1,i,imin,imax)
+      graddn = deriv(r,db,db2,-1,i,imin,imax)
+      gradd = gradup + graddn
+      return
+      end