diff --git a/pyxtal/interface/gulp.py b/pyxtal/interface/gulp.py
index 1d72fd6a..94992146 100644
--- a/pyxtal/interface/gulp.py
+++ b/pyxtal/interface/gulp.py
@@ -96,10 +96,9 @@
 }
 
 
-class GULP_OC:
+class GULP:
     """
-    A calculator to perform structure optimization in GULP
-    At the moment, only inorganic crystal is considered
+    A calculator to perform atomic structure optimization in GULP
 
     Args:
 
diff --git a/pyxtal/lego/builder.py b/pyxtal/lego/builder.py
index a116ea88..c7cb808e 100644
--- a/pyxtal/lego/builder.py
+++ b/pyxtal/lego/builder.py
@@ -1107,8 +1107,13 @@ def process_xtal(self, xtal, sim, count=0, xs=None, energy=None,
                'similarity': sim[1],
               }
         if xs is not None:
-            kvp['x_init'] = np.array2string(xs[0])
-            kvp['x_opt'] = np.array2string(xs[1])
+            try:
+                kvp['x_init'] = np.array2string(xs[0])
+                kvp['x_opt'] = np.array2string(xs[1])
+            except:
+                print("Error in xs", xs)
+                kvp['x_init'] = 'N/A'
+                kvp['x_opt'] = 'N/A'
         if energy is not None: kvp['ff_energy'] = energy
         if topology is not None: kvp['topology'] = topology
         if status: db.add_xtal(xtal, kvp)