Information on the convergence of the constraint fields.

Store the constraint fields from last iteration, write them to the
result file, and from that calculate the change of the fields.
Writes the maximum change and corresponding atom to output in each
iteration.

source/KKRnano/source/ProcessKKRresults_mod.F90

@@ -1131,10 +1131,10 @@ module ProcessKKRresults_mod
       reclen = max(reclen, 4*8 + 1*1 + 3*8)
     end if
     if (noncobfield) then
-      ! The constraint bfields, torques, and moments before fixing directions
-      ! (each double(3))
+      ! The constraint bfields (from this and from last iteration), torques,
+      ! and moments before fixing directions (each double(3))
       recnum = recnum + 1
-      reclen = max(reclen, (3+3+3)*8)
+      reclen = max(reclen, (3+3+3+3)*8)
     end if
 
   end subroutine
@@ -1206,8 +1206,11 @@ module ProcessKKRresults_mod
         irec = irec + 1
       endif
       if (params%noncobfield) then
-        write(unit=r1fu, rec=irec) calc%bfields(ila)%bfield_constr, &
-          calc%bfields(ila)%mag_torque, calc%bfields(ila)%mag_mom
+        write(unit=r1fu, rec=irec) &
+            calc%bfields(ila)%bfield_constr, &
+            calc%bfields(ila)%last_bfield_constr, &
+            calc%bfields(ila)%mag_torque, &
+            calc%bfields(ila)%mag_mom
         irec = irec + 1
       end if
     end do
@@ -1658,13 +1661,15 @@ module ProcessKKRresults_mod
     double precision delta_angle !NOCO
     integer :: max_delta_atom !NOCO
     double precision, dimension(3) :: dir ! NOCO, direction of local frame of reference
-    double precision, dimension(3) :: constr_field
+    double precision, dimension(3) :: constr_field, last_constr_field
     double precision, dimension(3) :: torque ! torque of the current atom
     double precision, dimension(3) :: newmoment ! magnetic moment before angle constraint
     double precision :: max_torque_sqrd      ! squared magnitude of largest torque so far
     integer :: max_torque_atom               ! atom with largest torque so far
     double precision :: constr_angle_change, max_constr_angle_change
     integer :: max_constr_angle_change_atom
+    double precision :: constr_field_change, max_constr_field_change
+    integer :: max_constr_field_change_atom
     integer :: reclen, recnum, irec, ie, lrecres2
     integer :: lcoremax, i1, ispin, lpot
     character(len=*), parameter :: &
@@ -1680,6 +1685,8 @@ module ProcessKKRresults_mod
     F82="('                    Largest torque magnitude [Ry] = ',E12.6)", &
     F83="('                    Largest change of angle for constraint moment at atom = ', i5)", &
     F84="('                    Largest change of angle for constraint moment (deg) = ', f10.6)", &
+    F85="('                    Largest change in constraint field at atom = ', i5)", &
+    F80="('                    Largest change in constraint field (Ry) = ', e10.4)", &
     F94="(4X,'nuclear charge  ',F10.6,9X,'core charge =   ',F10.6)"
     
     integer :: npotd
@@ -1694,6 +1701,8 @@ module ProcessKKRresults_mod
     max_torque_atom = 0
     max_constr_angle_change = 0.
     max_constr_angle_change_atom = -1 ! Initially a flag that means "feature not used (yet)"
+    max_constr_field_change = 0.
+    max_constr_field_change_atom = 0
 
     ! Calculate size of data written per atom
     call calculateResults1FileShapes(reclen, recnum, compute_total_energy, &
@@ -1776,7 +1785,7 @@ module ProcessKKRresults_mod
           irec = irec + 1
 
           if (noncobfield) then
-            read(71, rec=irec) constr_field, torque, newmoment
+            read(71, rec=irec) constr_field, last_constr_field, torque, newmoment
             irec = irec + 1
           end if
 
@@ -1831,6 +1840,17 @@ module ProcessKKRresults_mod
                 max_constr_angle_change = constr_angle_change
                 max_constr_angle_change_atom = i1
               end if
+
+              ! Look for largest change in constraining field
+              !   Reuse variable for difference
+              last_constr_field = last_constr_field - constr_field
+              !   Calculate the absolute value of the change (squared)
+              constr_field_change = dot_product(last_constr_field, last_constr_field)
+              if (constr_field_change > max_constr_field_change) then
+                ! Update
+                max_constr_field_change = constr_field_change
+                max_constr_field_change_atom = i1
+              end if
             end if
           end if
 
@@ -1882,6 +1902,8 @@ module ProcessKKRresults_mod
           if (max_constr_angle_change_atom >= 0) then
             write(6, fmt=F83) max_constr_angle_change_atom
             write(6, fmt=F84) 180.0/PI*max_constr_angle_change
+            write(6, fmt=F85) max_constr_field_change_atom
+            write(6, fmt=F80) sqrt(max_constr_field_change)
           end if
         end if
         write(6, '(79(1h+))')

source/KKRnano/source/bfield/bfield.f90

@@ -32,6 +32,7 @@ module mod_bfield
     ! Noncollinear magnetic fields
     double precision, dimension(3) :: bfield_ext    !! external magnetic field in cartesian coordinates
     double precision, dimension(3) :: bfield_constr !! constraining field in cartesian coordinates
+    double precision, dimension(3) :: last_bfield_constr !! constraining field of last iteration
 
     ! Torque and other information used to update the constraints fields
     double precision, dimension(3) :: mag_torque     !! Magnetic torque

source/KKRnano/source/bfield/torque.f90

@@ -183,6 +183,9 @@ contains
     mag_mom_dir = bfield%mag_mom(:) / mag_mom_len
     mag_mom_sign = sign(1., dot_product(mag_mom_dir, dir))
 
+    ! Save previous iterations field
+    bfield%last_bfield_constr = bfield%bfield_constr
+
     if (constr_mode == 3) then
       bfield%bfield_constr(:) = bfield%bfield_constr(:) - &
               ( mag_mom_sign * (bfield%mag_torque(:) / mag_mom_len) * &