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Commit a9947670 authored by Christopher Bruns's avatar Christopher Bruns
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Use either bond constraints or harmonic stretch, but not both, in HelloWaterBox.cpp

parent 9aaeed29
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Showing with 13 additions and 13 deletions
examples/HelloWaterBox.cpp
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......@@ -156,25 +156,25 @@ static void simulateWaterBox() {
0.0001 * OpenMM::NmPerAngstrom * SigmaPerVdwRadius,
0.0000 * OpenMM::KJPerKcal);
// Add stretch parameters for two covalent bonds
// Note factor of 2 for stiffness below because Amber specifies the constant
// as it is used in the harmonic energy term kx^2 with force 2kx; OpenMM wants
// it as used in the force term kx, with energy kx^2/2.
bondStretch.addBond(oIndex, h1Index,
0.9572 * OpenMM::NmPerAngstrom,
553.0 * 2 * OpenMM::KJPerKcal
* OpenMM::AngstromsPerNm * OpenMM::AngstromsPerNm);
bondStretch.addBond(oIndex, h2Index,
0.9572 * OpenMM::NmPerAngstrom,
553.0 * 2 * OpenMM::KJPerKcal
* OpenMM::AngstromsPerNm * OpenMM::AngstromsPerNm);
// constrain O-H bond lengths
if (UseConstraints) {
system.addConstraint(oIndex, h1Index,
0.9572 * OpenMM::NmPerAngstrom);
system.addConstraint(oIndex, h2Index,
0.9572 * OpenMM::NmPerAngstrom);
} else {
// Add stretch parameters for two covalent bonds
// Note factor of 2 for stiffness below because Amber specifies the constant
// as it is used in the harmonic energy term kx^2 with force 2kx; OpenMM wants
// it as used in the force term kx, with energy kx^2/2.
bondStretch.addBond(oIndex, h1Index,
0.9572 * OpenMM::NmPerAngstrom,
553.0 * 2 * OpenMM::KJPerKcal
* OpenMM::AngstromsPerNm * OpenMM::AngstromsPerNm);
bondStretch.addBond(oIndex, h2Index,
0.9572 * OpenMM::NmPerAngstrom,
553.0 * 2 * OpenMM::KJPerKcal
* OpenMM::AngstromsPerNm * OpenMM::AngstromsPerNm);
}
// Store bonds for exclusion list
......
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