Package etomica.spin.heisenberg

Class P2Spin

java.lang.Object

etomica.potential.Potential

etomica.potential.Potential2

etomica.spin.heisenberg.P2Spin

All Implemented Interfaces:

IPotential, IPotentialAtomic, IPotentialAtomicSecondDerivative, IPotentialTorque, PotentialSoft

public class P2Spin
extends Potential2
implements IPotentialTorque, IPotentialAtomicSecondDerivative

Magnetic spin potential, with an energy defined by

U = -J r1 dot r2

where J is a coupling parameter, and r1 and r2 are the vectors given by atom.coord.position. It is expected (but not verified here) that these vectors are normalized to unity, and that the simulation integrator's algorithm enforces this constraint.

Field Summary

Fields

Modifier and Type	Field	Description
protected Vector	dr
protected Vector	dr2
protected Tensor[]	secondDerivative
protected Vector[]	torque

Fields inherited from class etomica.potential.Potential

space

Constructor Summary

Constructors

Constructor	Description
P2Spin(Space space)
P2Spin(Space space, double coupling)

Method Summary

Modifier and Type	Method	Description
double	energy(IAtomList atoms)	Returns the energy for the given pair of atoms.
double	getCoupling()	* @return J the coupling parameter
double	getRange()	Returns 0, because potential operates on a lattice and range should not be needed.
Vector[]	gradient(IAtomList atoms)	do nothing
Vector[]	gradient(IAtomList atoms, Tensor pressureTensor)	do nothing
Vector[][]	gradientAndTorque(IAtomList atoms)
Vector[][]	gradientAndTorque(IAtomList atoms, Tensor pressureTensor)	do nothing
Tensor[]	secondDerivative(IAtomList atoms)	compute the secondDerivative array of pair energy w.r.t theta1 or theta2 i.e d^2u/dtheta1_dtheta1 d^2u/dtheta1_dtheta2 and d^2u/dtheta2_dtheta2 theta1 is the angle between x axis and atom1's orientation etc.
void	setBox(Box box)	does nothing
void	setCoupling(double coupling)	set the coupling parameter J
double	virial(IAtomList atoms)	no virial is use here

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

Field Detail

torque

protected final Vector[] torque

secondDerivative

protected final Tensor[] secondDerivative

dr

protected Vector dr

dr2

protected Vector dr2

Constructor Detail

P2Spin

public P2Spin(Space space)

P2Spin

public P2Spin(Space space,
              double coupling)

Method Detail

energy

public double energy(IAtomList atoms)

Returns the energy for the given pair of atoms.

Specified by:

energy in interface IPotentialAtomic

Specified by:

energy in class Potential

Parameters:

atoms -

Throws:

java.lang.ClassCastException - if atoms is not an instance of AtomPair

getRange

public double getRange()

Returns 0, because potential operates on a lattice and range should not be needed. The PotentialMasterSite expects all Potentials to have a range and uses the return value to determine whether or not to use site iteration.

Specified by:

getRange in interface IPotential

Specified by:

getRange in class Potential

getCoupling

public double getCoupling()

* @return J the coupling parameter

setCoupling

public void setCoupling(double coupling)

set the coupling parameter J

Parameters:

coupling -

setBox

public void setBox(Box box)

does nothing

Specified by:

setBox in interface IPotential

Specified by:

setBox in class Potential

Parameters:

box -

virial

public double virial(IAtomList atoms)

no virial is use here

Specified by:

virial in interface PotentialSoft

Throws:

java.lang.Exception - when virial is used

gradientAndTorque

public Vector[][] gradientAndTorque(IAtomList atoms)

Specified by:

gradientAndTorque in interface IPotentialTorque

Parameters:

atoms -

Returns:

gradient and torque of given pair of atoms

gradientAndTorque

public Vector[][] gradientAndTorque(IAtomList atoms,
                                    Tensor pressureTensor)

do nothing

secondDerivative

public Tensor[] secondDerivative(IAtomList atoms)

compute the secondDerivative array of pair energy w.r.t theta1 or theta2 i.e d^2u/dtheta1_dtheta1 d^2u/dtheta1_dtheta2 and d^2u/dtheta2_dtheta2 theta1 is the angle between x axis and atom1's orientation etc.

Specified by:

secondDerivative in interface IPotentialAtomicSecondDerivative

Parameters:

atoms - given pair of atoms

Returns:

secondDerivative array

gradient

public Vector[] gradient(IAtomList atoms)

do nothing

Specified by:

gradient in interface PotentialSoft

Returns:

gradient

public Vector[] gradient(IAtomList atoms,
                         Tensor pressureTensor)

do nothing

Specified by:

gradient in interface PotentialSoft