Added missing Born radii switching derivative

platforms/cuda/src/kernels/kForces.cu

@@ -380,6 +380,7 @@ void kReduceGBVIBornForces_kernel()
     {
         float bornRadius   = cSim.pBornRadii[pos];
         float4 gbviData    = cSim.pGBVIData[pos];
+        float  switchDeriv = cSim.pGBVISwitchDerivative[pos];
         float totalForce   = 0.0f;
         float* pFt         = cSim.pBornForce + pos;
 
@@ -416,7 +417,7 @@ void kReduceGBVIBornForces_kernel()
         energy             -= gbviData.z*ratio3;
         totalForce         += (3.0f*gbviData.z*ratio3)/bornRadius; // 'cavity' term
         float br2           = bornRadius*bornRadius;
-        totalForce         *= (1.0f/3.0f)*br2*br2;
+        totalForce         *= (1.0f/3.0f)*br2*br2*switchDeriv;
 
         pFt = cSim.pBornForce + pos;
         *pFt = totalForce;