Square loop option

src/opt_disl.f90

@@ -291,6 +291,21 @@ module opt_disl
             a3 = 3
         end select
 
+        if(loop_radius < 0.0_dp) then 
+                xLoop(:,:) = 0.d0
+                xLoop(1,a1) = centroid(1) - loop_radius
+                xLoop(1,a2) = centroid(2) - loop_radius
+                xLoop(1,a3) = centroid(3)
+                 xLoop(2,a1) = centroid(1) + loop_radius
+                 xLoop(2,a2) = centroid(2) - loop_radius
+                 xLoop(2,a3) = centroid(3)
+                xLoop(3,a1) = centroid(1) + loop_radius
+                xLoop(3,a2) = centroid(2) + loop_radius
+                xLoop(3,a3) = centroid(3)
+                 xLoop(4,a1) = centroid(1) - loop_radius
+                 xLoop(4,a2) = centroid(2) + loop_radius
+                 xLoop(4,a3) = centroid(3)
+        else
             !Calculate loop perimeter
             perimeter = 2.0_dp*pi*loop_radius
 
@@ -320,7 +335,7 @@ module opt_disl
                 ! Increment angle for next point
                 angle = angle + theta
             end do
-
+        end if
         !Now actually calculate the displacement created by a loop for every atom
         do i = 1, atom_num
             u = 0.0_dp