also copy cell to avoid future shenanigans

Author: svandenhaute

psiflow/functions.py

@@ -122,7 +122,7 @@ def geometry_to_key(geometry: Geometry) -> tuple:
 
             plumed_ = self.plumed_instances[key]
             if geometry.periodic:
-                cell = np.copy(geometry.cell).astype(np.float64)
+                cell = np.copy(geometry.cell).astype(np.float64).copy()
                 plumed_.cmd("setBox", cell)
 
             # set positions