diff --git a/_gridFunctions/derivative.py b/_gridFunctions/derivative.py
index 7aa0ead89b44084a9ef04ca6afefeb5ba6bace7e..441e78112855b30ee7569291e4c92e37edb2b17b 100644
--- a/_gridFunctions/derivative.py
+++ b/_gridFunctions/derivative.py
@@ -71,23 +71,6 @@ class Derivative:
     self.hs.Compute(solvetol)
   
   
-#-----------------------------------------------------------------------------#
-
-
-  def phiUniaxialAnisotropy(self, e):
-    from commics._tools.algebra import InnerProd
-    return -1.0 * InnerProd(e, self.gf) * e
-  
-  
-#-----------------------------------------------------------------------------#
-
-
-  def opZhangLi(self, vel):
-    return (sum(vel[k]*self.Dgf[0,k] for k in range(3)), \
-      sum(vel[k]*self.Dgf[1,k] for k in range(3)), \
-      sum(vel[k]*self.Dgf[2,k] for k in range(3)) )
-
-
 #-----------------------------------------------------------------------------#