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Commit 01d9e345 authored by peastman's avatar peastman Committed by GitHub
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Merge pull request #1504 from jlmaccal/fix_gb 

[WIP] Precompute GBNeck terms
parents 77b9b7ba b3471976
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Showing with 362 additions and 97 deletions
wrappers/python/simtk/openmm/app/charmmpsffile.py
View file @ 01d9e345
......@@ -1217,6 +1217,7 @@ class CharmmPsfFile(object):
else:
raise ValueError('Illegal nonbonded method for use with GBSA')
gb.setForceGroup(self.GB_FORCE_GROUP)
gb.finalize()
system.addForce(gb)
force.setReactionFieldDielectric(1.0) # applies to NonbondedForce
......
wrappers/python/simtk/openmm/app/internal/amber_file_parser.py
View file @ 01d9e345
......@@ -1006,8 +1006,8 @@ def readAmberSystem(topology, prmtop_filename=None, prmtop_loader=None, shake=No
for i, (r, s) in enumerate(zip(radii, screen)):
if abs(r - gb_parms[i][0]) > 1e-4 or abs(s - gb_parms[i][1]) > 1e-4:
if not warned:
warnings.warn('Non-optimal GB parameters detected for GB '
'model %s' % gbmodel)
warnings.warn(
'Non-optimal GB parameters detected for GB model %s' % gbmodel)
warned = True
gb_parms[i][0], gb_parms[i][1] = r, s
......@@ -1019,7 +1019,13 @@ def readAmberSystem(topology, prmtop_filename=None, prmtop_loader=None, shake=No
gb_parm[2], gb_parm[3], gb_parm[4]])
else:
gb.addParticle([charge, gb_parm[0], gb_parm[1]])
# OBC2 with kappa == 0 uses mm.GBSAOBC2Force, which doesn't have
# a finalize method
if not (gbmodel == 'OBC2' and implicitSolventKappa == 0.):
gb.finalize()
system.addForce(gb)
if nonbondedMethod == 'NoCutoff':
gb.setNonbondedMethod(mm.NonbondedForce.NoCutoff)
elif nonbondedMethod == 'CutoffNonPeriodic':
......
wrappers/python/simtk/openmm/app/internal/customgbforces.py
View file @ 01d9e345
......@@ -6,9 +6,9 @@ Simbios, the NIH National Center for Physics-Based Simulation of
Biological Structures at Stanford, funded under the NIH Roadmap for
Medical Research, grant U54 GM072970. See https://simtk.org.
Portions copyright (c) 2012-2015 University of Virginia and the Authors.
Portions copyright (c) 2012-2016 University of Virginia and the Authors.
Authors: Christoph Klein, Michael R. Shirts
Contributors: Jason M. Swails, Peter Eastman
Contributors: Jason M. Swails, Peter Eastman, Justin L. MacCallum
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
......@@ -29,19 +29,25 @@ OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
USE OR OTHER DEALINGS IN THE SOFTWARE.
"""
from __future__ import division, absolute_import
from collections import defaultdict
import copy
from simtk.openmm.app import element as E
from simtk.openmm import CustomGBForce, Continuous2DFunction
from simtk.openmm import CustomGBForce, Discrete2DFunction
import simtk.unit as u
from math import floor
def strip_unit(value, unit):
"""Strip off any units and return value in unit"""
if not u.is_quantity(value):
return value
return value.value_in_unit(unit)
# GBn and GBn2 lookup tables
d0=[2.26685,2.32548,2.38397,2.44235,2.50057,2.55867,2.61663,2.67444,
2.73212,2.78965,2.84705,2.9043,2.96141,3.0184,3.07524,3.13196,
3.18854,3.24498,3.30132,3.35752,3.4136,
......@@ -106,8 +112,6 @@ d0=[2.26685,2.32548,2.38397,2.44235,2.50057,2.55867,2.61663,2.67444,
3.6629,3.71694,3.77095,3.82489,3.8788,3.93265,3.98646,4.04022,
4.09395,4.14762,4.20126,4.25485,4.3084]
m0=[0.0381511,0.0338587,0.0301776,0.027003,0.0242506,0.0218529,
0.0197547,0.0179109,0.0162844,0.0148442,0.0135647,0.0124243,
0.0114047,0.0104906,0.00966876,0.008928,0.0082587,0.00765255,
......@@ -192,10 +196,10 @@ m0=[0.0381511,0.0338587,0.0301776,0.027003,0.0242506,0.0218529,
0.0332033,0.030322,0.0277596,0.0254732,0.0234266,0.0215892,
0.0199351,0.018442,0.0170909,0.0158654,0.0147514,0.0137365,
0.0128101,0.0119627,0.0111863]
# Rescale to nm
for i in range (len(d0)):
d0[i]=d0[i]/10
m0[i]=m0[i]*10
# Rescale to nanometers
d0 = [d / 10. for d in d0]
m0 = [m * 10. for m in m0]
def _get_bonded_atom_list(topology):
""" Returns a list of atoms bonded to each other atom in a dict """
......@@ -205,6 +209,7 @@ def _get_bonded_atom_list(topology):
bondeds[a2].append(a1)
return bondeds
def _is_carboxylateO(atom, all_bonds):
if atom is not E.oxygen: return False
bondeds = all_bonds[atom]
......@@ -224,6 +229,7 @@ def _is_carboxylateO(atom, all_bonds):
# If we got here, must be a carboxylate
return True
def _bondi_radii(topology):
""" Sets the bondi radii """
radii = [0.0 for atom in topology.atoms()]
......@@ -250,6 +256,7 @@ def _bondi_radii(topology):
radii[i] = 1.5
return radii # converted to nanometers above
def _mbondi_radii(topology):
""" Sets the mbondi radii """
radii = [0.0 for atom in topology.atoms()]
......@@ -286,6 +293,7 @@ def _mbondi_radii(topology):
radii[i] = 1.5
return radii # converted to nanometers above
def _mbondi2_radii(topology):
""" Sets the mbondi2 radii """
radii = [0.0 for atom in topology.atoms()]
......@@ -320,6 +328,7 @@ def _mbondi2_radii(topology):
radii[i] = 1.5
return radii # Converted to nanometers above
def _mbondi3_radii(topology):
""" Sets the mbondi3 radii """
radii = _mbondi2_radii(topology)
......@@ -333,9 +342,13 @@ def _mbondi3_radii(topology):
radii[i] = 1.17
return radii # Converted to nanometers above
def _createEnergyTerms(force, solventDielectric, soluteDielectric, SA, cutoff, kappa, offset):
# Add the energy terms to the CustomGBForce. These are identical for all the GB models.
"""Add the energy terms to the CustomGBForce.
These are identical for all the GB models.
"""
params = "; solventDielectric=%.16g; soluteDielectric=%.16g; kappa=%.16g; offset=%.16g" % (solventDielectric, soluteDielectric, kappa, offset)
if cutoff is not None:
params += "; cutoff=%.16g" % cutoff
......@@ -367,6 +380,7 @@ def _createEnergyTerms(force, solventDielectric, soluteDielectric, SA, cutoff, k
force.addEnergyTerm("-138.935485*(1/soluteDielectric-1/solventDielectric)*q1*q2*(1/f-"+str(1/cutoff)+");"
"f=sqrt(r^2+B1*B2*exp(-r^2/(4*B1*B2)))"+params, CustomGBForce.ParticlePairNoExclusions)
_SCREEN_PARAMETERS = { # normal, GBn, GBn2
E.hydrogen : (0.85, 1.09085413633, 1.425952),
E.carbon : (0.72, 0.48435382330, 1.058554),
......@@ -377,33 +391,52 @@ _SCREEN_PARAMETERS = { # normal, GBn, GBn2
E.sulfur : (0.96, 0.602256336067, -0.703469),
None : (0.8, 0.5, 0.5) # default
}
_SCREEN_PARAMETERS[E.deuterium] = _SCREEN_PARAMETERS[E.hydrogen]
def _screen_parameter(atom):
if atom.element in _SCREEN_PARAMETERS:
return _SCREEN_PARAMETERS[atom.element]
return _SCREEN_PARAMETERS[None]
class CustomAmberGBForce(CustomGBForce):
class CustomAmberGBForceBase(CustomGBForce):
"""Base class for all of the Amber custom GB forces.
Should not be instantiated directly, use one of its
derived classes instead.
"""
OFFSET = 0.009
RADIUS_ARG_POSITION = 1
SCREEN_POSITION = 2
def __init__(self, *args, **kwargs):
raise NotImplementedError('Cannot instantiate ABC')
def __init__(self):
CustomGBForce.__init__(self)
self.parameters = []
def addParticle(self, params):
params = copy.deepcopy(params)
params[self.RADIUS_ARG_POSITION] = strip_unit(params[self.RADIUS_ARG_POSITION], u.nanometer) - self.OFFSET
params[self.SCREEN_POSITION] *= params[self.RADIUS_ARG_POSITION]
CustomGBForce.addParticle(self, params)
return params
"""Add a particle to the force
Particles are added in order. The number of particles
added must match the number of particles in the system.
Parameters
----------
params : list
A list of parameters to add to the force. The meaning
parameters depends on the model.
def setParticleParameters(self, idx, params):
Returns
-------
list
The list of parameters after stripping off units and
modifying SCREEN.
"""
params = copy.deepcopy(params)
params[self.RADIUS_ARG_POSITION] = strip_unit(params[self.RADIUS_ARG_POSITION], u.nanometer) - self.OFFSET
params[self.SCREEN_POSITION] *= params[self.RADIUS_ARG_POSITION]
CustomGBForce.addParticle(self, params)
self.parameters.append(params)
return params
@staticmethod
......@@ -421,17 +454,50 @@ class CustomAmberGBForce(CustomGBForce):
List of all parameters needed for this GB model. These can be passed
to addParticle or setParticleParameters after the charge is inserted
at the beginning of the list
"""
raise NotImplementedError('Must override getStandardParameters in subclasses')
raise NotImplementedError(
'getStandardParameters must be defined in derived classes')
"""
Amber Equivalent: igb = 1
"""
class GBSAHCTForce(CustomAmberGBForce):
def finalize(self):
"""Finalize this force so it can be added to a system.
This method must be called before the force is added
to the system.
"""
self._addParticles()
def _addParticles(self):
for params in self.parameters:
CustomGBForce.addParticle(self, params)
class GBSAHCTForce(CustomAmberGBForceBase):
"""This class is equivalent to Amber ``igb=1``
The list of parameters to ``addParticle`` is: ``[q, or, sr]``.
Parameters
----------
solventDielectric: float
Dielectric constant for the solvent
soluteDielectric: float
Dielectric constant for the solute
SA: string or None
Surface area model to use
cutoff: float or Quantity or None
Cutoff distance to use. If float, value is in nm. If ``None``,
then no cutoffs are used.
kappa: float or Quantity
Debye kappa parameter related to modelling salt in GB. It has
units of 1 / length with 1 / nanometer assumed if a float
is given. A value of zero corresponds to zero salt concentration.
"""
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None,
cutoff=None, kappa=0.0):
CustomGBForce.__init__(self)
CustomAmberGBForceBase.__init__(self)
self.addPerParticleParameter("q")
self.addPerParticleParameter("or") # Offset radius
......@@ -447,20 +513,53 @@ class GBSAHCTForce(CustomAmberGBForce):
@staticmethod
def getStandardParameters(topology):
""" Gets list of standard parameters for this GB model based on an input Topology
Parameters
----------
topology : simtk.openmm.app.Topology
Topology of the system to get parameters for
Returns
-------
list of float
List of all parameters needed for this GB model. These can be passed
to addParticle or setParticleParameters after the charge is inserted
at the beginning of the list
"""
radii = [[x/10] for x in _mbondi_radii(topology)]
for i, atom in enumerate(topology.atoms()):
radii[i].append(_screen_parameter(atom)[0])
return radii
"""
Amber Equivalents: igb = 2
"""
class GBSAOBC1Force(CustomAmberGBForce):
class GBSAOBC1Force(CustomAmberGBForceBase):
"""This class is equivalent to Amber ``igb=2``
The list of parameters to ``addParticle`` is: ``[q, or, sr]``.
Parameters
----------
solventDielectric: float
Dielectric constant for the solvent
soluteDielectric: float
Dielectric constant for the solute
SA: string or None
Surface area model to use
cutoff: float or Quantity or None
Cutoff distance to use. If float, value is in nm. If ``None``,
then no cutoffs are used.
kappa: float or Quantity
Debye kappa parameter related to modelling salt in GB. It has
units of 1 / length with 1 / nanometer assumed if a float
is given. A value of zero corresponds to zero salt concentration.
"""
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None,
cutoff=None, kappa=0.0):
CustomGBForce.__init__(self)
CustomAmberGBForceBase.__init__(self)
self.addPerParticleParameter("q")
self.addPerParticleParameter("or") # Offset radius
......@@ -476,20 +575,55 @@ class GBSAOBC1Force(CustomAmberGBForce):
@staticmethod
def getStandardParameters(topology):
""" Gets list of standard parameters for this GB model based on an input Topology
Parameters
----------
topology : simtk.openmm.app.Topology
Topology of the system to get parameters for
Returns
-------
list of float
List of all parameters needed for this GB model. These can be passed
to addParticle or setParticleParameters after the charge is inserted
at the beginning of the list
"""
radii = [[x/10] for x in _mbondi2_radii(topology)]
for i, atom in enumerate(topology.atoms()):
radii[i].append(_screen_parameter(atom)[0])
return radii
"""
Amber Equivalents: igb = 5
"""
class GBSAOBC2Force(GBSAOBC1Force):
class GBSAOBC2Force(GBSAOBC1Force):
"""This class is equivalent to Amber ``igb=5``
The list of parameters to ``addParticle`` is: ``[q, or, sr]``.
Parameters
----------
solventDielectric: float
Dielectric constant for the solvent
soluteDielectric: float
Dielectric constant for the solute
SA: string or None
Surface area model to use
cutoff: float or Quantity or None
Cutoff distance to use. If float, value is in nm. If ``None``,
then no cutoffs are used.
kappa: float or Quantity
Debye kappa parameter related to modelling salt in GB. It has
units of 1 / length with 1 / nanometer assumed if a float
is given. A value of zero corresponds to zero salt concentration.
"""
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None,
cutoff=None, kappa=0.0):
CustomGBForce.__init__(self)
# Note that this is not GBSAOBC1Force, as our initialization
# is different. We inherit for getStandardParameters.
CustomAmberGBForceBase.__init__(self)
self.addPerParticleParameter("q")
self.addPerParticleParameter("or") # Offset radius
......@@ -503,90 +637,185 @@ class GBSAOBC2Force(GBSAOBC1Force):
"psi=I*or; radius=or+offset; offset=0.009", CustomGBForce.SingleParticle)
_createEnergyTerms(self, solventDielectric, soluteDielectric, SA, cutoff, kappa, 0.009)
"""
Amber Equivalents: igb = 7
"""
class GBSAGBnForce(CustomAmberGBForce):
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None,
cutoff=None, kappa=0.0):
CustomGBForce.__init__(self)
self.addPerParticleParameter("q")
self.addPerParticleParameter("or") # Offset radius
self.addPerParticleParameter("sr") # Scaled offset radius
self.addTabulatedFunction("getd0", Continuous2DFunction(21, 21, d0, 0.1, 0.2, 0.1, 0.2))
self.addTabulatedFunction("getm0", Continuous2DFunction(21, 21, m0, 0.1, 0.2, 0.1, 0.2))
class GBSAGBnForce(CustomAmberGBForceBase):
"""This class is equivalent to Amber ``igb=7``
The list of parameters to ``addParticle`` is: ``[q, or, sr]``.
Parameters
----------
solventDielectric: float
Dielectric constant for the solvent
soluteDielectric: float
Dielectric constant for the solute
SA: string or None
Surface area model to use
cutoff: float or Quantity or None
Cutoff distance to use. If float, value is in nm. If ``None``,
then no cutoffs are used.
kappa: float or Quantity
Debye kappa parameter related to modelling salt in GB. It has
units of 1 / length with 1 / nanometer assumed if a float
is given. A value of zero corresponds to zero salt concentration.
"""
OFFSET = 0.009
self.addComputedValue("I", "Ivdw+neckScale*Ineck;"
"Ineck=step(radius1+radius2+neckCut-r)*getm0(radius1,radius2)/(1+100*(r-getd0(radius1,radius2))^2+0.3*1000000*(r-getd0(radius1,radius2))^6);"
"Ivdw=step(r+sr2-or1)*0.5*(1/L-1/U+0.25*(r-sr2^2/r)*(1/(U^2)-1/(L^2))+0.5*log(L/U)/r);"
"U=r+sr2;"
"L=max(or1, D);"
"D=abs(r-sr2);"
"radius1=or1+offset; radius2=or2+offset;"
"neckScale=0.361825; neckCut=0.68; offset=0.009", CustomGBForce.ParticlePairNoExclusions)
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None, cutoff=None, kappa=0.0):
self.addComputedValue("B", "1/(1/or-tanh(1.09511284*psi-1.907992938*psi^2+2.50798245*psi^3)/radius);"
"psi=I*or; radius=or+offset; offset=0.009", CustomGBForce.SingleParticle)
_createEnergyTerms(self, solventDielectric, soluteDielectric, SA, cutoff, kappa, 0.009)
CustomAmberGBForceBase.__init__(self)
self.solventDielectric = solventDielectric
self.soluteDielectric = soluteDielectric
self.SA = SA
self.cutoff = cutoff
self.kappa = kappa
self._uniqueRadii = None
self._radiusToIndex = None
def addParticle(self, parameters):
parameters = CustomAmberGBForce.addParticle(self, parameters)
parameters = CustomAmberGBForceBase.addParticle(self, parameters)
if parameters[1] + self.OFFSET < 0.1 or parameters[1] + self.OFFSET > 0.2:
raise ValueError('Radii must be between 1 and 2 Angstroms for neck lookup')
def setParticleParameters(self, idx, parameters):
parameters = CustomAmberGBForce.setParticleParameters(self, idx, parameters)
if parameters[1] < 0.1 or parameters[1] > 0.2:
raise ValueError('Radii must be between 1 and 2 Angstroms for neck lookup')
def finalize(self):
self._findUniqueRadii()
self._createRadiusToIndexMap()
self._addEnergyTerms()
self._addParticles()
@staticmethod
def getStandardParameters(topology):
""" Gets list of standard parameters for this GB model based on an input Topology
Parameters
----------
topology : simtk.openmm.app.Topology
Topology of the system to get parameters for
Returns
-------
list of float
List of all parameters needed for this GB model. These can be passed
to addParticle or setParticleParameters after the charge is inserted
at the beginning of the list
"""
radii = [[x/10] for x in _bondi_radii(topology)]
for i, atom in enumerate(topology.atoms()):
radii[i].append(_screen_parameter(atom)[1])
return radii
"""
Amber Equivalents: igb = 8
"""
class GBSAGBn2Force(GBSAGBnForce):
OFFSET = 0.0195141
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None,
cutoff=None, kappa=0.0):
CustomGBForce.__init__(self)
def _findUniqueRadii(self):
radii = [p[self.RADIUS_ARG_POSITION] for p in self.parameters]
self._uniqueRadii = list(sorted(set(radii)))
def _createRadiusToIndexMap(self):
self._radiusToIndex = {r: i for i, r in enumerate(self._uniqueRadii)}
def _createUniqueTable(self, fullTable):
tablePositions = [(r+self.OFFSET-0.1)*200 for r in self._uniqueRadii]
numRadii = len(self._uniqueRadii)
index1 = [0]*numRadii
index2 = [0]*numRadii
weight1 = [0]*numRadii
weight2 = [0]*numRadii
for i,p in enumerate(tablePositions):
if p <= 0:
weight1[i] = 1.0
elif p >= 20:
index1[i] = 20
weight1[i] = 1.0
else:
index1[i] = int(floor(p))
index2[i] = index1[i]+1
weight1[i] = index2[i]-p
weight2[i] = 1.0-weight1[i]
table = []
for i in range(numRadii):
for j in range(numRadii):
table.append(weight1[i]*weight1[j]*fullTable[index1[i]*21+index1[j]] +
weight1[i]*weight2[j]*fullTable[index1[i]*21+index2[j]] +
weight2[i]*weight1[j]*fullTable[index2[i]*21+index1[j]] +
weight2[i]*weight2[j]*fullTable[index2[i]*21+index2[j]])
return table
def _addParticles(self):
for p in self.parameters:
radIndex = self._radiusToIndex[p[self.RADIUS_ARG_POSITION]]
CustomGBForce.addParticle(self, p + [radIndex])
def _addEnergyTerms(self):
self.addPerParticleParameter("q")
self.addPerParticleParameter("or") # Offset radius
self.addPerParticleParameter("sr") # Scaled offset radius
self.addPerParticleParameter("alpha")
self.addPerParticleParameter("beta")
self.addPerParticleParameter("gamma")
self.addPerParticleParameter("radindex")
n = len(self._uniqueRadii)
m0Table = self._createUniqueTable(m0)
d0Table = self._createUniqueTable(d0)
self.addTabulatedFunction("getd0", Discrete2DFunction(n, n, d0Table))
self.addTabulatedFunction("getm0", Discrete2DFunction(n, n, m0Table))
self.addComputedValue("I", "Ivdw+neckScale*Ineck;"
"Ineck=step(radius1+radius2+neckCut-r)*getm0(radindex1,radindex2)/(1+100*(r-getd0(radindex1,radindex2))^2+"
"0.3*1000000*(r-getd0(radindex1,radindex2))^6);"
"Ivdw=step(r+sr2-or1)*0.5*(1/L-1/U+0.25*(r-sr2^2/r)*(1/(U^2)-1/(L^2))+0.5*log(L/U)/r);"
"U=r+sr2;"
"L=max(or1, D);"
"D=abs(r-sr2);"
"radius1=or1+offset; radius2=or2+offset;"
"neckScale=0.361825; neckCut=0.68; offset=0.009", CustomGBForce.ParticlePairNoExclusions)
self.addTabulatedFunction("getd0", Continuous2DFunction(21, 21, d0, 0.1, 0.2, 0.1, 0.2))
self.addTabulatedFunction("getm0", Continuous2DFunction(21, 21, m0, 0.1, 0.2, 0.1, 0.2))
self.addComputedValue("B", "1/(1/or-tanh(1.09511284*psi-1.907992938*psi^2+2.50798245*psi^3)/radius);"
"psi=I*or; radius=or+offset; offset=0.009", CustomGBForce.SingleParticle)
_createEnergyTerms(self, self.solventDielectric, self.soluteDielectric, self.SA, self.cutoff, self.kappa, self.OFFSET)
self.addComputedValue("I", "Ivdw+neckScale*Ineck;"
"Ineck=step(radius1+radius2+neckCut-r)*getm0(radius1,radius2)/(1+100*(r-getd0(radius1,radius2))^2+0.3*1000000*(r-getd0(radius1,radius2))^6);"
"Ivdw=step(r+sr2-or1)*0.5*(1/L-1/U+0.25*(r-sr2^2/r)*(1/(U^2)-1/(L^2))+0.5*log(L/U)/r);"
"U=r+sr2;"
"L=max(or1, D);"
"D=abs(r-sr2);"
"radius1=or1+offset; radius2=or2+offset;"
"neckScale=0.826836; neckCut=0.68; offset=0.0195141", CustomGBForce.ParticlePairNoExclusions)
self.addComputedValue("B", "1/(1/or-tanh(alpha*psi-beta*psi^2+gamma*psi^3)/radius);"
"psi=I*or; radius=or+offset; offset=0.0195141", CustomGBForce.SingleParticle)
_createEnergyTerms(self, solventDielectric, soluteDielectric, SA, cutoff, kappa, 0.0195141)
class GBSAGBn2Force(GBSAGBnForce):
"""This class is equivalent to Amber ``igb=8``
The list of parameters to ``addParticle`` is: ``[q, or, sr, alpha, beta, gamma]``.
Parameters
----------
solventDielectric: float
Dielectric constant for the solvent
soluteDielectric: float
Dielectric constant for the solute
SA: string or None
Surface area model to use
cutoff: float or Quantity or None
Cutoff distance to use. If float, value is in nm. If ``None``,
then no cutoffs are used.
kappa: float or Quantity
Debye kappa parameter related to modelling salt in GB. It has
units of 1 / length with 1 / nanometer assumed if a float
is given. A value of zero corresponds to zero salt concentration.
"""
OFFSET = 0.0195141
def __init__(self, solventDielectric=78.5, soluteDielectric=1, SA=None, cutoff=None, kappa=0.0):
GBSAGBnForce.__init__(self, solventDielectric, soluteDielectric, SA, cutoff, kappa)
@staticmethod
def getStandardParameters(topology):
""" Gets list of standard parameters for this GB model based on an input Topology
Parameters
----------
topology : simtk.openmm.app.Topology
Topology of the system to get parameters for
Returns
-------
list of float
List of all parameters needed for this GB model. These can be passed
to addParticle or setParticleParameters after the charge is inserted
at the beginning of the list
"""
radii = [[x/10] for x in _mbondi3_radii(topology)]
for i, atom in enumerate(topology.atoms()):
radii[i].append(_screen_parameter(atom)[2])
......@@ -603,3 +832,32 @@ class GBSAGBn2Force(GBSAGBnForce):
else:
radii[i].extend([0.8, 4.85, 0.5])
return radii
def _addEnergyTerms(self):
self.addPerParticleParameter("q")
self.addPerParticleParameter("or") # Offset radius
self.addPerParticleParameter("sr") # Scaled offset radius
self.addPerParticleParameter("alpha")
self.addPerParticleParameter("beta")
self.addPerParticleParameter("gamma")
self.addPerParticleParameter("radindex")
n = len(self._uniqueRadii)
m0Table = self._createUniqueTable(m0)
d0Table = self._createUniqueTable(d0)
self.addTabulatedFunction("getd0", Discrete2DFunction(n, n, d0Table))
self.addTabulatedFunction("getm0", Discrete2DFunction(n, n, m0Table))
self.addComputedValue("I", "Ivdw+neckScale*Ineck;"
"Ineck=step(radius1+radius2+neckCut-r)*getm0(radindex1,radindex2)/(1+100*(r-getd0(radindex1,radindex2))^2+"
"0.3*1000000*(r-getd0(radindex1,radindex2))^6);"
"Ivdw=step(r+sr2-or1)*0.5*(1/L-1/U+0.25*(r-sr2^2/r)*(1/(U^2)-1/(L^2))+0.5*log(L/U)/r);"
"U=r+sr2;"
"L=max(or1, D);"
"D=abs(r-sr2);"
"radius1=or1+offset; radius2=or2+offset;"
"neckScale=0.826836; neckCut=0.68; offset=0.0195141", CustomGBForce.ParticlePairNoExclusions)
self.addComputedValue("B", "1/(1/or-tanh(alpha*psi-beta*psi^2+gamma*psi^3)/radius);"
"psi=I*or; radius=or+offset; offset=0.0195141", CustomGBForce.SingleParticle)
_createEnergyTerms(self, self.solventDielectric, self.soluteDielectric, self.SA, self.cutoff, self.kappa, self.OFFSET)
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