point_charges
Include effects of point charges through electrostatic, and possibly van der Waals, interactions with QM atoms.
Periodic point charge embedding is only compatible with GFN1xTB and is activated by including the lattice subcommand. This command can appear in the global context.
Subcommands
Options
charges

Charges for each particle defined by xyz
 The type is [real]
 There is no default value.
coupling_scheme

Specify the coupling scheme between QM and MM subsystems.
 The type is string
 The default is electrostatic
 The value must be one of:
oniom
 Use the ONIOM coupling scheme.mechanical
 Use the mechanical coupling scheme.electrostatic
 Use the electrostatic coupling scheme.
ewald_alpha

Broadening parameter for Gaussian screening of point charges in Ewald treatment of second and third order terms of xTB Hamiltonian. This effectively determines the relative contributions of realspace and reciprocalspace terms in the Ewald sum. As \(\alpha\) is increased, ewald_real_cutoff should be decreased, while ewald_reciprocal_cutoff should be increased. By default, entos determines this from ewald_real_cutoff and ewald_relative_error, using the expression: \( \alpha = \frac{1}{r_c} \bigg[ W \bigg( \frac{Q}{E}\sqrt{\frac{r_c}{2V}} \bigg) \bigg]^{1/2}, \) where \(r_c\) is the ewald_real_cutoff, \(E\) is the ewald_relative_error, \( Q = \sum^{N_{atoms}}_{i=1} q_i^2 \), \(\{q_i\}\) are atomic partial charges of neutral atoms, \(W\) is the Lambert W function, and \(V\) is the system volume. This approximation is not guaranteed to give ideal results, but it works fairly well for most systems. Further details can be found in A comparison of the Spectral Ewald and Smooth Particle Mesh Ewald methods in GROMACS.
 The type is real
 There is no default value.
ewald_real_cutoff

Realspace cutoff over unit cells in Ewald sum.
 The type is quantity
 There is no default value.
ewald_reciprocal_cutoff

Reciprocalspace cutoff over kvectors in Ewald sum. By default, entos determines this from ewald_real_cutoff and ewald_relative_error, using the expression: \( k_c = \frac{\sqrt{3} L \alpha}{2 \pi} \bigg[ W \bigg( \frac{4}{3L^2} \bigg(\frac{Q^2}{\pi \alpha E^2}\bigg)^{2/3} \bigg) \bigg]^{1/2} \) where \(\alpha\) is the ewald_alpha, \(E\) is the ewald_relative_error, \( Q = \sum^{N_{atoms}}_{i=1} q_i^2 \), \(\{q_i\}\) are atomic partial charges of neutral atoms, \(W\) is the Lambert W function, and \(L\) is the average system length. This approximation is not guaranteed to give ideal results, but it works fairly well for most systems. Further details can be found in A comparison of the Spectral Ewald and Smooth Particle Mesh Ewald methods in GROMACS.
 The type is real
 There is no default value.
file

Specify name of the file containing MM point charges. The format of a pointcharge file should be: the first line containing the number of point charges, and each of the remaining lines containing the charge and the xyz coordinates (in Angstrom). For example, the following file specifies three point charges:
3 0.123 0.0000 0.0000 0.0000 2.345 1.0000 1.0000 0.0000 3.456 1.0000 1.0000 0.0000  The type is string
 There is no default value.
xyz

Positions of charges
 The type is [(real, real, real)]
 There is no default value.