diff --git a/src/pair_zbl.cpp b/src/pair_zbl.cpp
index a9882f1fe7..c44c9542b4 100644
--- a/src/pair_zbl.cpp
+++ b/src/pair_zbl.cpp
@@ -240,6 +240,10 @@ void PairZBL::init_style()
 
   cut_innersq = cut_inner * cut_inner;
   cut_globalsq = cut_global * cut_global;
+  // metal units: e^2/angstrom = 2*Ryd*bohr
+  // econv = 2.0*13.6058*0.529177 = 14.3998;
+  // all units:
+  econv = force->qqr2e;
 }
 
 /* ----------------------------------------------------------------------
@@ -273,9 +277,17 @@ double PairZBL::init_one(int i, int j)
   // sw1 = A 
   // sw2 = B 
 
+  // de2dr2 = 2*A*t + 3*B*t^2
+
+  // Require that at t = tc:
+  // e = -Fc
+  // dedr = -Fc'
+  // d2edr2 = -Fc'' 
+
+  // Hence:
   // A = (-3Fc' + tc*Fc'')/tc^2
   // B = ( 2Fc' - tc*Fc'')/tc^3
-  // C = = -Fc + tc/2*Fc' - tc^2/12*Fc''
+  // C = -Fc + tc/2*Fc' - tc^2/12*Fc''
 
   double tc = cut_global - cut_inner;
   double fc = e_zbl(cut_global, i, j);
diff --git a/src/pair_zbl.h b/src/pair_zbl.h
index 690ae8107d..c93106369f 100644
--- a/src/pair_zbl.h
+++ b/src/pair_zbl.h
@@ -37,7 +37,7 @@ class PairZBL : public Pair {
 
  protected:
   double cut_global, cut_inner;
-  double cut_globalsq, cut_innersq;
+  double cut_globalsq, cut_innersq, econv;
   double *z;
   double **d1a,**d2a,**d3a,**d4a,**zze;
   double **sw1,**sw2,**sw3,**sw4,**sw5;
@@ -62,10 +62,6 @@ namespace PairZBLConstants {
   static const double d2 = 0.40290;
   static const double d3 = 0.94229;
   static const double d4 = 3.19980;
-
-  //  units: e^2/angstrom = 2*Ryd*bohr
-
-  static const double econv = 2.0*13.6058*0.529177;
 }
 
 }