Faunus::pairpotential::CosAttract Class Reference

Cosine attraction. More...

#include <potentials.h>

Inheritance diagram for Faunus::pairpotential::CosAttract:

Collaboration diagram for Faunus::pairpotential::CosAttract:

Public Member Functions
	CosAttract (const std::string &name="cos2")
double	cutOffSquared () const
	Squared cutoff distance where potential goes to zero.
double	operator() (const Particle &, const Particle &, double squared_distance, const Point &) const override
Point	force (const Particle &, const Particle &, double squared_distance, const Point &b_towards_a) const override
	Force on particle a due to particle b. More...
void	to_json (json &j) const override

Additional Inherited Members
Public Attributes inherited from Faunus::pairpotential::PairPotential
std::string	name
	unique name per polymorphic call; used in FunctorPotential::combinePairPotentials
std::string	cite
	Typically a short-doi litterature reference.
bool	isotropic = true
	true if pair-potential is independent of particle orientation
std::function< double(const Particle &)>	selfEnergy = nullptr
	self energy of particle (kT)
Protected Member Functions inherited from Faunus::pairpotential::PairPotential
	PairPotential (std::string name=std::string(), std::string cite=std::string(), bool isotropic=true)

Detailed Description

Cosine attraction.

This is an attractive potential used for coarse grained lipids and has the form:

\[ \beta u(r) = -\epsilon \cos^2 [ \pi(r-r_c)/2w_c ] \]

for \(r_c\leq r \leq r_c+w_c\). For \(r<r_c\), \(\beta u=-\epsilon\), while zero for \(r>r_c+w_c\).

JSON keywords:

Key	Description
eps	Depth, \(\epsilon\) [kJ/mol]
rc	Width, r_c [angstrom]
wc	Decay range, w_c [angstrom]

Member Function Documentation

force()

Point Faunus::pairpotential::CosAttract::force ( const Particle &  a, const Particle &  b, double  squared_distance, const Point &  b_towards_a  ) const

inlineoverridevirtual

Force on particle a due to particle b.

Calculates force on particle a due to another particle, b.

Parameters

particle_a	First particle
particle_b	Second particle
squared_distance	Squared distance, |𝐚-𝐛|²
b_towards_a	Distance vector 𝐛 -> 𝐚 = 𝐚 - 𝐛

Returns

Force acting on a dur to b in units of kT/Å

Parameters

particle_a	Particle a
particle_b	Particle b
squared_distance	Squared norm |𝐚-𝐛|²
b_towards_a	Distance vector 𝐛 -> 𝐚 = 𝐚 - 𝐛

Returns

Force on particle a due to particle b

Reimplemented from Faunus::pairpotential::PairPotential.

operator()()

double Faunus::pairpotential::CosAttract::operator() ( const Particle &  , const Particle &  , double  squared_distance, const Point &    ) const

inlineoverridevirtual

Todo:

The function x(c,r2,rc) defined herein could be approximated by a series expansion for r2=rcwc2.

In this way one can avoid cos() and sqrt(). C code for this could be generated in Matlab:

with(CodeGeneration)
x := series(cos(c*(sqrt(r2)-rc)), r2 = rcwc2, 2)
convert(x, polynom)
C(%, resultname = "x")

Implements Faunus::pairpotential::PairPotential.

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The documentation for this class was generated from the following files:

• src/potentials.h
• src/potentials.cpp