Source code for dxtb._src.param.hamiltonian

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"""
Parametrization: Hamiltonian
============================

Definition of the global core Hamiltonian parameters.

The core Hamiltonian is rescaling the shell-blocks of the overlap integrals
formed over the basis set by the average of the atomic self-energies and an
additional distance dependent function formed from the element parametrization.
"""

from __future__ import annotations

from typing import Dict, Optional

from pydantic import BaseModel

__all__ = ["Hamiltonian", "XTBHamiltonian"]


class ShellScaling(BaseModel):
    """
    Shell-dependent scaling factor for the off-site blocks
    """

    ss: float
    """Scaling factor for two s-shells."""

    pp: float
    """Scaling factor for two p-shells."""

    dd: float
    """Scaling factor for two d-shells."""

    sd: float
    """Scaling factor for an s- and a d-shell."""

    pd: float
    """Scaling factor for a p- and a d-shell."""




class XTBHamiltonian(BaseModel):
    """
    Global parameters for the formation of the core Hamiltonian from the
    overlap integrals. Contains the required atomic and shell dependent scaling
    parameters to obtain the off-site scaling functions independent of the
    self-energy and the distance polynomial.
    """

    wexp: float
    """Exponent of the orbital exponent dependent off-site scaling factor"""

    kpol: float = 2.0
    """Scaling factor for polarization functions"""

    enscale: float
    """Electronegativity scaling factor for off-site valence blocks"""

    cn: Optional[str] = None
    """Local environment descriptor for shifting the atomic self-energies"""

    shell: Dict[str, float]
    """Shell-pair dependent scaling factor for off-site blocks"""

    kpair: Dict[str, float] = {}
    """Atom-pair dependent scaling factor for off-site valence blocks"""





class Hamiltonian(BaseModel):
    """
    Possible Hamiltonian parametrizations.
    Currently only the xTB Hamiltonian is supported.
    """

    xtb: XTBHamiltonian
    """Data for the xTB Hamiltonian"""