# ChargeScreened¶

class ChargeScreened : public feasst::ModelTwoBody

Compute energy between two point charges, $$q_i$$ and $$q_j$$ with a Gaussian screening cloud as utilized by the Ewald summation.

$$U = q_i q_j \chi erfc(\alpha r)/r$$

where $$erfc$$ is the complimentary error function, $$r$$ is the separation distance, and $$\chi$$ is the charge conversion factor assuming the following units:

1. length: Angstroms

2. energy: kJ/mol

3. charge: elementary

Avoid Coulomb explosion by returning a large number when $$r$$ is near zero.

Public Functions

ChargeScreened(const argtype &args = argtype())

args:

• disable_table: if true, do not use a tabular erfc (default: false).

• hard_sphere_threshold: return NEAR_INFINITY when distance is less than this threshold (default: 0.1).

void precompute(const ModelParams &existing)

Precompute model parameters based on existing model parameters.

const Table1D *erfc(const double distance_squared) const

Return the erfc table.

void serialize(std::ostream &ostr) const

Output a serialized version of the existing model.