--- trunk/OOPSE/libmdtools/NPTi.cpp	2003/09/19 14:55:41	770
+++ trunk/OOPSE/libmdtools/NPTi.cpp	2003/09/19 16:01:07	772
@@ -13,7 +13,6 @@
 #include "mpiSimulation.hpp"
 #endif
 
-
 // Basic isotropic thermostating and barostating via the Melchionna
 // modification of the Hoover algorithm:
 //
@@ -88,9 +87,8 @@ template<typename T> void NPTi<T>::moveA() {
     mass = atoms[i]->getMass();
 
     for (j=0; j < 3; j++) {
-      // velocity half step  (use chi from previous step here):
+      // velocity half step 
       vel[j] += dt2 * ((frc[j] / mass ) * eConvert - vel[j]*(chi + eta));
-  
     }
 
     atoms[i]->setVel( vel );
@@ -142,14 +140,18 @@ template<typename T> void NPTi<T>::moveA() {
     }    
   }
 
-  // evolve chi and eta  half step
+  // advance chi half step
   
   chi += dt2 * ( instaTemp / targetTemp - 1.0) / tt2;
-  eta += dt2 * ( instaVol * (instaPress - targetPressure) / (p_convert*NkBT*tb2));
 
-  //calculate the integral of chidt
+  // calculate the integral of chidt
+
   integralOfChidt += dt2*chi;
 
+  // advance eta half step
+
+  eta += dt2 * ( instaVol * (instaPress - targetPressure) / (p_convert*NkBT*tb2));
+
   //save the old positions
   for(i = 0; i < nAtoms; i++){
     atoms[i]->getPos(pos);
@@ -208,10 +210,10 @@ template<typename T> void NPTi<T>::moveB( void ){
   double vel[3], frc[3];
   double mass;
 
-  double instTemp, instPress, instVol;
+  double instaTemp, instaPress, instaVol;
   double tt2, tb2;
   double oldChi, prevChi;
-  double oldEta, preEta;
+  double oldEta, prevEta;
   
   tt2 = tauThermostat * tauThermostat;
   tb2 = tauBarostat * tauBarostat;
@@ -242,21 +244,23 @@ template<typename T> void NPTi<T>::moveB( void ){
 
   // do the iteration:
 
-  instVol = tStats->getVolume();
+  instaVol = tStats->getVolume();
   
   for (k=0; k < 4; k++) {
     
-    instTemp = tStats->getTemperature();
-    instPress = tStats->getPressure();
+    instaTemp = tStats->getTemperature();
+    instaPress = tStats->getPressure();
 
     // evolve chi another half step using the temperature at t + dt/2
 
     prevChi = chi;
-    chi = oldChi + dt2 * ( instTemp / targetTemp - 1.0) / 
-      (tauThermostat*tauThermostat);
+    chi = oldChi + dt2 * ( instaTemp / targetTemp - 1.0) / tt2;
 
-    preEta = eta;
-    eta = oldEta + dt2 * ( instVol * (instPress - targetPressure) / 
+    prevEta = eta;
+
+    // advance eta half step and calculate scale factor for velocity
+
+    eta = oldEta + dt2 * ( instaVol * (instaPress - targetPressure) / 
        (p_convert*NkBT*tb2));
 
   
@@ -294,14 +298,13 @@ template<typename T> void NPTi<T>::moveB( void ){
     }    
     
     if (fabs(prevChi - chi) <= 
-	chiTolerance && fabs(preEta -eta) <= etaTolerance) 
+	chiTolerance && fabs(prevEta -eta) <= etaTolerance) 
       break;
   }
 
-  //calculate integral of chida
+  //calculate integral of chidt
   integralOfChidt += dt2*chi;
 
-
 }
 
 template<typename T> void NPTi<T>::resetIntegrator() {