Source code for tad_dftd4.dispersion.d4

# This file is part of tad-dftd4.
#
# SPDX-Identifier: Apache-2.0
# Copyright (C) 2024 Grimme Group
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# Licensed under the Apache License, Version 2.0 (the "License");
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#     http://www.apache.org/licenses/LICENSE-2.0
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"""
Dispersion Methods: D4
======================

DFT-D4 dispersion method implementation.
"""

from __future__ import annotations

from ..damping import RationalDamping, ZeroDamping
from .base import Disp
from .threebody import ATM, C9ApproxMixin, C9ExactMixin, RadiiBJMixin
from .twobody import TwoBodyTerm

__all__ = ["DispD4"]


class _DispD4(Disp):
    """Standard DFT-D4 dispersion method."""

    ALLOWED_MODELS = ("d4", "d4s")
    """Allowed DFT-D models for the calculation."""


##############################################################################


class D4ATMApprox(C9ApproxMixin, RadiiBJMixin, ATM):
    """D4 ATM: approximate C9 + Becke-Johnson radii."""




class DispD4(_DispD4):
    """Standard DFT-D4 dispersion method."""

    TERMS = [
        (
            TwoBodyTerm,
            {"damping_fn": RationalDamping(), "charge_dependent": True},
        ),
        (
            D4ATMApprox,
            {"damping_fn": ZeroDamping(), "charge_dependent": False},
        ),
    ]
    """List of dispersion terms to be registered in the constructor."""



##############################################################################


class D4ATMExact(C9ExactMixin, RadiiBJMixin, ATM):
    """D4 ATM: approximate C9 + Becke-Johnson radii."""


class DispD4Exact(Disp):
    """DFT-D4 with exact C9 coefficients via Casimir--Polder formula."""

    TERMS = [
        (
            TwoBodyTerm,
            {"damping_fn": RationalDamping(), "charge_dependent": True},
        ),
        (
            D4ATMExact,
            {"damping_fn": ZeroDamping(), "charge_dependent": False},
        ),
    ]
    """List of dispersion terms to be registered in the constructor."""