Package etomica.potential

Class P2SquareWell

java.lang.Object

etomica.potential.Potential

etomica.potential.Potential2

etomica.potential.Potential2HardSpherical

etomica.potential.P2SquareWell

All Implemented Interfaces:

IPotential, IPotentialAtomic, Potential2Spherical, PotentialHard

Direct Known Subclasses:

P2SquareWellBonded, P2SquareWellBonded, P2SquareWellMonomer, P2SquareWellRadical

public class P2SquareWell
extends Potential2HardSpherical

Basic square-well potential. Energy is infinite if spheres overlap, is -epsilon if less than lambda*sigma and not overlapping, and is zero otherwise. Core diameter describes size of hard core; lambda is multiplier to get range of well. Suitable for use in space of any dimension. Can be used with negative value for epsilon to produce square-shoulder potential. This implementation determines which atoms are interacting (in the well) by checking their distance. This is prone to numerical roundoff issues, and so atoms are bumped off the well after capture and escape. This can cause issues related to 3-particle collisions. P2SquareWellRobust can be used instead to avoid such issues.

Field Summary

Fields

Modifier and Type	Field	Description
protected double	coreDiameter
protected double	coreDiameterSquared
protected Vector	dv
protected double	epsilon
protected boolean	ignoreOverlap
protected double	lambda
protected double	lastCollisionVirial
protected double	lastCollisionVirialr2
protected Tensor	lastCollisionVirialTensor
protected double	lastEnergyChange
protected double	wellDiameter
protected double	wellDiameterSquared

Fields inherited from class etomica.potential.Potential

space

Fields inherited from class etomica.potential.Potential2HardSpherical

boundary, dr

Constructor Summary

Constructors

Constructor	Description
P2SquareWell(Space space)
P2SquareWell(Space space, double coreDiameter, double lambda, double epsilon, boolean ignoreOverlap)

Method Summary

Modifier and Type	Method	Description
void	bump(IAtomList pair, double falseTime)	Implements collision dynamics between two square-well atoms.
double	collisionTime(IAtomList pair, double falseTime)	Computes next time of collision of two square-well atoms, assuming free-flight kinematics.
double	energyChange()	returns change in potential energy due to the last collision
double	getCoreDiameter()	Accessor method for core diameter.
Dimension	getCoreDiameterDimension()
double	getEpsilon()	Accessor method for depth of well
Dimension	getEpsilonDimension()
double	getLambda()	Accessor method for well-diameter multiplier.
Dimension	getLambdaDimension()
double	getRange()	Returns the range over which the potential applies.
double	lastCollisionVirial()	Value of the virial from the most recent collision.
Tensor	lastCollisionVirialTensor()	Value of the virial from the most recent collision, decomposed into it tensoral elements.
void	setCoreDiameter(double c)	Accessor method for core diameter.
void	setEpsilon(double eps)	Accessor method for depth of well
void	setLambda(double lam)	Accessor method for well-diameter multiplier.
double	u(double r2)	Returns infinity if overlapping, -epsilon if otherwise less than well diameter, or zero if neither.

Methods inherited from interface etomica.potential.IPotential

nBody

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from class etomica.potential.Potential

nBody

Methods inherited from class etomica.potential.Potential2HardSpherical

energy, setBox

Field Detail

coreDiameter

protected double coreDiameter

coreDiameterSquared

protected double coreDiameterSquared

wellDiameter

protected double wellDiameter

wellDiameterSquared

protected double wellDiameterSquared

lambda

protected double lambda

epsilon

protected double epsilon

lastCollisionVirial

protected double lastCollisionVirial

lastCollisionVirialr2

protected double lastCollisionVirialr2

lastCollisionVirialTensor

protected Tensor lastCollisionVirialTensor

lastEnergyChange

protected double lastEnergyChange

dv

protected Vector dv

ignoreOverlap

protected final boolean ignoreOverlap

Constructor Detail

P2SquareWell

public P2SquareWell(Space space)

P2SquareWell

public P2SquareWell(Space space,
                    double coreDiameter,
                    double lambda,
                    double epsilon,
                    boolean ignoreOverlap)

Method Detail

getRange

public double getRange()

Description copied from interface: IPotential

Returns the range over which the potential applies. IAtoms with a greater separation do not interact.

Specified by:

getRange in interface IPotential

Specified by:

getRange in class Potential

bump

public void bump(IAtomList pair,
                 double falseTime)

Implements collision dynamics between two square-well atoms. Includes all possibilities involving collision of hard cores, and collision of wells both approaching and diverging

lastCollisionVirial

public double lastCollisionVirial()

Description copied from interface: PotentialHard

Value of the virial from the most recent collision.

Returns:

double virial value

lastCollisionVirialTensor

public Tensor lastCollisionVirialTensor()

Description copied from interface: PotentialHard

Value of the virial from the most recent collision, decomposed into it tensoral elements.

Returns:

Tensor

collisionTime

public double collisionTime(IAtomList pair,
                            double falseTime)

Computes next time of collision of two square-well atoms, assuming free-flight kinematics. Collision may occur when cores collides, or when wells first encounter each other on approach, or when they edge of the wells are reached as atoms diverge.

u

public double u(double r2)

Returns infinity if overlapping, -epsilon if otherwise less than well diameter, or zero if neither.

Specified by:

u in interface Potential2Spherical

Specified by:

u in class Potential2HardSpherical

Parameters:

r2 - the square of the distance between the particles.

energyChange

public double energyChange()

Description copied from interface: PotentialHard

returns change in potential energy due to the last collision

getCoreDiameter

public double getCoreDiameter()

Accessor method for core diameter.

setCoreDiameter

public void setCoreDiameter(double c)

Accessor method for core diameter. Well diameter is defined as a multiple (lambda) of this, and is updated when core diameter is changed

getCoreDiameterDimension

public Dimension getCoreDiameterDimension()

getLambda

public double getLambda()

Accessor method for well-diameter multiplier.

setLambda

public void setLambda(double lam)

Accessor method for well-diameter multiplier. Well diameter is defined as this multiple of core diameter, and is updated when this is changed

getLambdaDimension

public Dimension getLambdaDimension()

getEpsilon

public double getEpsilon()

Accessor method for depth of well

setEpsilon

public void setEpsilon(double eps)

Accessor method for depth of well

getEpsilonDimension

public Dimension getEpsilonDimension()