Implementation of dpd.hpp. More...

#include "config/config.hpp"
#include "dpd.hpp"
#include "BoxGeometry.hpp"
#include "cell_system/CellStructure.hpp"
#include "cells.hpp"
#include "nonbonded_interactions/nonbonded_interaction_data.hpp"
#include "random.hpp"
#include "system/System.hpp"
#include "thermostat.hpp"
#include <utils/Vector.hpp>
#include <utils/constants.hpp>
#include <utils/math/sqr.hpp>
#include <utils/math/tensor_product.hpp>
#include <utils/matrix.hpp>
#include <boost/mpi/collectives/reduce.hpp>
#include <algorithm>
#include <cmath>
#include <cstdint>
#include <functional>

Include dependency graph for dpd.cpp:

Go to the source code of this file.

Functions
Utils::Vector3d	dpd_noise (DPDThermostat const &dpd, int pid1, int pid2)
	Return a random uniform 3D vector with the Philox thermostat.

void	dpd_init (double kT, double time_step)

static double	weight (int type, double r_cut, double k, double r)

Utils::Vector3d	dpd_pair_force (DPDParameters const &params, Utils::Vector3d const &v, double dist, Utils::Vector3d const &noise)

Utils::Vector3d	dpd_pair_force (Particle const &p1, Particle const &p2, DPDThermostat const &dpd, BoxGeometry const &box_geo, IA_parameters const &ia_params, Utils::Vector3d const &d, double dist, double dist2)

static auto	dpd_viscous_stress_local ()

Utils::Vector9d	dpd_stress (boost::mpi::communicator const &comm)
	Viscous stress tensor of the DPD interaction.

Detailed Description

Implementation of dpd.hpp.

Definition in file dpd.cpp.

Function Documentation

◆ dpd_init()

void dpd_init	(	double	kT,
		double	time_step
	)

Definition at line 64 of file dpd.cpp.

References System::get_system(), and System::System::nonbonded_ias.

Referenced by Thermostat::Thermostat::recalc_prefactors().

◆ dpd_noise()

Utils::Vector3d dpd_noise	(	DPDThermostat const &	dpd,
		int	pid1,
		int	pid2
	)

Return a random uniform 3D vector with the Philox thermostat.

Random numbers depend on

dpd_rng_counter (initialized by seed) which is increased on integration
Salt (decorrelates different counters)
Two particle IDs (order-independent, decorrelates particles, gets rid of seed-per-node)

Definition at line 58 of file dpd.cpp.

References BaseThermostat::rng_counter(), and BaseThermostat::rng_seed().

Referenced by dpd_pair_force().

◆ dpd_pair_force() [1/2]

Utils::Vector3d dpd_pair_force	(	DPDParameters const &	params,
		Utils::Vector3d const &	v,
		double	dist,
		Utils::Vector3d const &	noise
	)

Definition at line 86 of file dpd.cpp.

References SteepestDescentParameters::gamma, params, Utils::sqr(), and weight().

Referenced by add_non_bonded_pair_force(), dpd_pair_force(), dpd_viscous_stress_local(), and Constraints::ShapeBasedConstraint::force().

◆ dpd_pair_force() [2/2]

Utils::Vector3d dpd_pair_force	(	Particle const &	p1,
		Particle const &	p2,
		DPDThermostat const &	dpd,
		BoxGeometry const &	box_geo,
		IA_parameters const &	ia_params,
		Utils::Vector3d const &	d,
		double	dist,
		double	dist2
	)

Definition at line 103 of file dpd.cpp.

References DPDParameters::cutoff, IA_parameters::dpd, dpd_noise(), dpd_pair_force(), force, Particle::id(), P, Particle::pos(), DPDParameters::pref, DPD_Parameters::radial, DPD_Parameters::trans, Particle::v(), and BoxGeometry::velocity_difference().

◆ dpd_stress()

Utils::Vector9d dpd_stress ( boost::mpi::communicator const & comm )

Viscous stress tensor of the DPD interaction.

This calculates the total viscous stress contribution of the DPD interaction. It contains only the dissipative contributions of the interaction without noise. It's calculated as the sum over all pair virials as

\[ \sigma^{\nu\mu} = V^{-1}\sum_i \sum_{j < i} r_{i,j}^{\nu} (- \gamma_{i,j} v_{i,j})^{\mu} \]

where \(\gamma_{i,j}\) is the (in general tensor valued) DPD friction coefficient for particles i and j, \(v_{i,j}\), \(r_{i,j}\) are their relative velocity and distance and \(V\) is the box volume.