ppmd.coulomb.ewald module

Methods for Coulombic forces and energies with the classical Ewald method.

class ppmd.coulomb.ewald.EwaldOrthoganal(domain, eps=1e-06, real_cutoff=None, alpha=None, recip_cutoff=None, recip_nmax=None, shared_memory=False, shell_width=None, work_ratio=1.0, force_unit=1.0, energy_unit=1.0)

Bases: object

alpha

alpha

evaluate_contributions(positions, charges)

evaluate_self_interactions(charges, energy=None, potential=None)

extract_forces_energy_real(positions, charges, forces, energy=None, potential=None)

extract_forces_energy_reciprocal(positions, charges, forces, energy, potential=None)

static internal_to_ev()

Multiply by this constant to convert from internal units to eV.

kmax

Number of reciporcal vectors taken in each direction.

real_cutoff

Real space cutoff

recip_cutoff

Reciprocal space cutoff.

recip_vectors

Reciprocal lattice vectors

shell_width

Real space padding width

test_evaluate_python_lr(positions, charges)

test_evaluate_python_self(charges)

test_evaluate_python_sr(positions, charges)

ppmd.coulomb.ewald.EwaldOrthogonal

alias of ppmd.coulomb.ewald.EwaldOrthoganal

ppmd.coulomb.ewald.compute_alpha(N, L, ratio)

Compute an optimal alpha to give O(N^{3/2}) scaling for ewald summation. tau_r: Real space time cost per pair of particles (time cost per real space kernel executin) tau_f: Time for reciprocal component per particle per reciprocal vector. :param N: Number of particles :param L: Domain extent (assumes cubic) :param ratio: ratio: tau_r/tau_f. :return: optimal alpha

ppmd.coulomb.ewald.compute_rc_nc_cutoff(alpha, L, eps=1e-06)