qimpy.grid.Coulomb

class Coulomb(grid, n_ions)

Bases: object

Coulomb interactions between fields and point charges. TODO: support non-periodic geometries (truncation).

Parameters

grid (Grid) –
n_ions (int) –

__init__(grid, n_ions)

Initialize coulomb interactions.

Parameters

grid (Grid) – Fields for coulomb interaction will be on this grid.
n_ions (int) – Number of point charges to optimize Ewald sums for.

Return type

None

Methods

`__init__`	Initialize coulomb interactions.
`ewald`	Compute Ewald energy, and optionally accumulate gradients.
`stress`	Return stress due to Coulomb interaction between rho1 and rho2.
`update_lattice_dependent`	Update all members that depend on lattice vectors.

Attributes

`grid`	Grid associated with fields for coulomb interaction
`ion_width`	Ion-charge gaussian width for embedding and solvation
`sigma`	Ewald range-separation parameter
`iR`	Ewald real-space mesh points
`iG`	Ewald reciprocal-space mesh points

ewald(positions, Z)

Compute Ewald energy, and optionally accumulate gradients. Each gradient contribution is accumulated to a grad attribute, only if the corresponding requires_grad is enabled. Force contributions are collected in positions.grad. Stress contributions are collected in self.grid.lattice.grad.

Parameters

positions (Tensor) – Positions (fractional coordinates) of point charges
Z (Tensor) – Charges of each point charge

Return type

float

stress(rho1, rho2)

Return stress due to Coulomb interaction between rho1 and rho2. The result has dimensions of energy, appropriate for adding to lattice.grad.

Parameters

rho1 (FieldH) –
rho2 (FieldH) –

Return type

Tensor

update_lattice_dependent(n_ions)

Update all members that depend on lattice vectors.

Parameters: n_ions (int) –
Return type: None

grid: Grid: Grid associated with fields for coulomb interaction

iG: Tensor: Ewald reciprocal-space mesh points

iR: Tensor: Ewald real-space mesh points

ion_width: float: Ion-charge gaussian width for embedding and solvation

sigma: float: Ewald range-separation parameter