diff --git a/lib/colvars/colvar.cpp b/lib/colvars/colvar.cpp
index c662982080..128762cb06 100644
--- a/lib/colvars/colvar.cpp
+++ b/lib/colvars/colvar.cpp
@@ -98,8 +98,8 @@ colvar::colvar (std::string const &conf)
                          "on an axis",       "distanceZ",      distance_z);
   initialize_components ("distance projection "
                          "on a plane",       "distanceXY",     distance_xy);
-  initialize_components ("average distance weighted by inverse sixth power",
-                         "distance6", distance6);
+  initialize_components ("average distance weighted by inverse power",
+                         "distanceInv", distance_inv);
 
   initialize_components ("coordination "
                          "number",           "coordNum",       coordnum);
diff --git a/lib/colvars/colvar.h b/lib/colvars/colvar.h
index a9542a606c..396c63dc5a 100644
--- a/lib/colvars/colvar.h
+++ b/lib/colvars/colvar.h
@@ -471,7 +471,7 @@ public:
   class distance;
   class distance_z;
   class distance_xy;
-  class distance6;
+  class distance_inv;
   class angle;
   class dihedral;
   class coordnum;
diff --git a/lib/colvars/colvaratoms.h b/lib/colvars/colvaratoms.h
index 481a93a9bd..782ae6b9c8 100644
--- a/lib/colvars/colvaratoms.h
+++ b/lib/colvars/colvaratoms.h
@@ -1,3 +1,5 @@
+// -*- c++ -*-
+
 #ifndef COLVARATOMS_H
 #define COLVARATOMS_H
 
@@ -304,15 +306,8 @@ public:
   /// the colvar has not a scalar value) or the biases require to
   /// micromanage the forces.
   void apply_forces (std::vector<cvm::rvector> const &forces);
+
 };
 
 
-
-
 #endif
-
-
-// Emacs
-// Local Variables:
-// mode: C++
-// End:
diff --git a/lib/colvars/colvarcomp.h b/lib/colvars/colvarcomp.h
index 00d333dc89..7954fb5c1d 100644
--- a/lib/colvars/colvarcomp.h
+++ b/lib/colvars/colvarcomp.h
@@ -470,16 +470,16 @@ public:
 
 /// \brief Colvar component: average distance between two groups of atoms, weighted as the sixth power,
 /// as in NMR refinements (colvarvalue::type_scalar type, range (0:*))
-class colvar::distance6
+class colvar::distance_inv
   : public colvar::distance
 {
 protected:
   /// Components of the distance vector orthogonal to the axis
-  cvm::real smoothing;
+  int exponent;
 public:
-  distance6 (std::string const &conf);
-  distance6();
-  virtual inline ~distance6() {}
+  distance_inv (std::string const &conf);
+  distance_inv();
+  virtual inline ~distance_inv() {}
   virtual void calc_value();
   virtual void calc_gradients();
   virtual void apply_force (colvarvalue const &force);
@@ -1296,7 +1296,7 @@ inline void colvar::spin_angle::wrap (colvarvalue &x) const
   simple_scalar_dist_functions (distance)
   // NOTE: distance_z has explicit functions, see below 
   simple_scalar_dist_functions (distance_xy)
-  simple_scalar_dist_functions (distance6)
+  simple_scalar_dist_functions (distance_inv)
   simple_scalar_dist_functions (angle)
   simple_scalar_dist_functions (coordnum)
   simple_scalar_dist_functions (selfcoordnum)
diff --git a/lib/colvars/colvarcomp_distances.cpp b/lib/colvars/colvarcomp_distances.cpp
index 2b46538564..35d29efe4b 100644
--- a/lib/colvars/colvarcomp_distances.cpp
+++ b/lib/colvars/colvarcomp_distances.cpp
@@ -454,25 +454,34 @@ void colvar::distance_dir::apply_force (colvarvalue const &force)
 
 
 
-colvar::distance6::distance6 (std::string const &conf)
+colvar::distance_inv::distance_inv (std::string const &conf)
   : distance (conf)
 {
-  function_type = "distance6";
+  function_type = "distance_inv";
+  get_keyval (conf, "exponent", exponent, 6);
+  if (exponent%2) {
+    cvm::fatal_error ("Error: odd exponent provided, can only use even ones.\n");
+  }
+  if (exponent <= 0) {
+    cvm::fatal_error ("Error: negative or zero exponent provided.\n");
+  }
+
   b_inverse_gradients = false;
   b_Jacobian_derivative = false;
   x.type (colvarvalue::type_scalar);
 }
 
-colvar::distance6::distance6()
+colvar::distance_inv::distance_inv()
 {
-  function_type = "distance6";
+  function_type = "distance_inv";
+  exponent = 6;
   b_inverse_gradients = false;
   b_Jacobian_derivative = false;
   b_1site_force = false;
   x.type (colvarvalue::type_scalar);
 }
 
-void colvar::distance6::calc_value()
+void colvar::distance_inv::calc_value()
 {
   group1.reset_atoms_data();
   group2.reset_atoms_data();
@@ -486,8 +495,11 @@ void colvar::distance6::calc_value()
       for (cvm::atom_iter ai2 = group2.begin(); ai2 != group2.end(); ai2++) {
         cvm::rvector const dv = ai2->pos - ai1->pos;
         cvm::real const d2 = dv.norm2();
-        x.real_value += 1.0/(d2*d2*d2);
-        cvm::rvector const dsumddv = -6.0/(d2*d2*d2*d2) * dv;
+        cvm::real dinv = 1.0;
+        for (int ne = 0; ne < exponent/2; ne++)
+          dinv *= 1.0/d2;
+        x.real_value += dinv;
+        cvm::rvector const dsumddv = -(cvm::real (exponent)) * dinv/d2 * dv;
         ai1->grad += -1.0 * dsumddv;
         ai2->grad +=        dsumddv;
       }
@@ -497,8 +509,11 @@ void colvar::distance6::calc_value()
       for (cvm::atom_iter ai2 = group2.begin(); ai2 != group2.end(); ai2++) {
         cvm::rvector const dv = cvm::position_distance (ai1->pos, ai2->pos);
         cvm::real const d2 = dv.norm2();
-        x.real_value += 1.0/(d2*d2*d2);
-        cvm::rvector const dsumddv = -6.0/(d2*d2*d2*d2) * dv;
+        cvm::real dinv = 1.0;
+        for (int ne = 0; ne < exponent/2; ne++)
+          dinv *= 1.0/d2;
+        x.real_value += dinv;
+        cvm::rvector const dsumddv = -(cvm::real (exponent)) * dinv/d2 * dv;
         ai1->grad += -1.0 * dsumddv;
         ai2->grad +=        dsumddv;
       }
@@ -506,12 +521,12 @@ void colvar::distance6::calc_value()
   }
 
   x.real_value *= 1.0 / cvm::real (group1.size() * group2.size());
-  x.real_value = std::pow (x.real_value, -1.0/6.0);
+  x.real_value = std::pow (x.real_value, -1.0/(cvm::real (exponent)));
 }
 
-void colvar::distance6::calc_gradients()
+void colvar::distance_inv::calc_gradients()
 {
-  cvm::real const dxdsum = (-1.0/6.0) * std::pow (x.real_value, 7.0) / cvm::real (group1.size() * group2.size());
+  cvm::real const dxdsum = (-1.0/(cvm::real (exponent))) * std::pow (x.real_value, exponent+1) / cvm::real (group1.size() * group2.size());
   for (cvm::atom_iter ai1 = group1.begin(); ai1 != group1.end(); ai1++) {
     ai1->grad *= dxdsum;
   }
@@ -520,7 +535,7 @@ void colvar::distance6::calc_gradients()
   }
 }
 
-void colvar::distance6::apply_force (colvarvalue const &force)
+void colvar::distance_inv::apply_force (colvarvalue const &force)
 {
   if (!group1.noforce)
     group1.apply_colvar_force (force.real_value);
diff --git a/lib/colvars/colvarmodule.h b/lib/colvars/colvarmodule.h
index f587f6a321..2dfc1bd2ac 100644
--- a/lib/colvars/colvarmodule.h
+++ b/lib/colvars/colvarmodule.h
@@ -2,7 +2,7 @@
 #define COLVARMODULE_H
 
 #ifndef COLVARS_VERSION
-#define COLVARS_VERSION "2012-07-17"
+#define COLVARS_VERSION "2012-08-08"
 #endif
 
 #ifndef COLVARS_DEBUG