# Copyright 2021-2023 @ Shenzhen Bay Laboratory &
# Peking University &
# Huawei Technologies Co., Ltd
#
# This code is a part of MindSPONGE:
# MindSpore Simulation Package tOwards Next Generation molecular modelling.
#
# MindSPONGE is open-source software based on the AI-framework:
# MindSpore (https://www.mindspore.cn/)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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# See the License for the specific language governing permissions and
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# ============================================================================
"""Berendsen thermostat"""
from typing import Tuple
from mindspore import Tensor
from mindspore import ops
from .thermostat import Thermostat, _thermostat_register
from ...system import Molecule
from ...function import get_arguments
[docs]@_thermostat_register('berendsen')
class BerendsenThermostat(Thermostat):
r"""
A Berendsen (weak coupling) thermostat module, which is a subclass of :class:`sponge.control.Thermostat`.
Reference Berendsen, H. J. C.; Postma, J. P. M.; van Gunsteren, W. F.; DiNola, A.; Haak, J. R..
Molecular Dynamics with Coupling to an External Bath [J].
The Journal of Chemical Physics, 1984, 81(8).
Args:
system (:class: `sponge.system.Molecule`): Simulation system.
temperature (float, optional): Reference temperature :math:`T_{ref}`
in unit Kelvin for temperature coupling.
Default: ``300.0``.
control_step (int, optional): Step interval for controller execution.
Default: ``1``.
time_constant (float, optional): Time constant :math:`\tau_T`
in unit picosecond for temperature coupling.
Default: ``0.5``.
scale_min (float, optional): The minimum value to clip the velocity scale factor.
Default: ``0.8``.
scale_max (float, optional): The maximum value to clip the velocity scale factor.
Default: ``1.25``.
Inputs:
- **coordinate** (Tensor) - Coordinate. Tensor of shape :math:`(B, A, D)`.
Data type is float.
Here :math:`B` is the number of walkers in simulation,
:math:`A` is the number of atoms and
:math:`D` is the spatial dimension of the simulation system, which is usually 3.
- **velocity** (Tensor) - Velocity. Tensor of shape :math:`(B, A, D)`. Data type is float.
- **force** (Tensor) - Force. Tensor of shape :math:`(B, A, D)`. Data type is float.
- **energy** (Tensor) - Energy. Tensor of shape :math:`(B, 1)`. Data type is float.
- **kinetics** (Tensor) - Kinetics. Tensor of shape :math:`(B, D)`. Data type is float.
- **virial** (Tensor) - Virial. Tensor of shape :math:`(B, D)`. Data type is float.
- **pbc_box** (Tensor) - Pressure boundary condition box. Tensor of shape :math:`(B, D)`.
Data type is float.
- **step** (int) - Simulation step. Default: ``0``.
Outputs:
- coordinate, Tensor of shape :math:`(B, A, D)`. Coordinate. Data type is float.
- velocity, Tensor of shape :math:`(B, A, D)`. Velocity. Data type is float.
- force, Tensor of shape :math:`(B, A, D)`. Force. Data type is float.
- energy, Tensor of shape :math:`(B, 1)`. Energy. Data type is float.
- kinetics, Tensor of shape :math:`(B, D)`. Kinetics. Data type is float.
- virial, Tensor of shape :math:`(B, D)`. Virial. Data type is float.
- pbc_box, Tensor of shape :math:`(B, D)`. Periodic boundary condition box.
Data type is float.
Supported Platforms:
``Ascend`` ``GPU``
Examples:
>>> from sponge import Molecule
>>> from sponge.control import BerendsenThermostat
>>> system = Molecule(template='water.tip3p.yaml')
>>> controller = BerendsenThermostat(system)
"""
def __init__(self,
system: Molecule,
temperature: float = 300,
control_step: int = 1,
time_constant: float = 0.5,
scale_min: float = 0.8,
scale_max: float = 1.25,
**kwargs,
):
super().__init__(
system=system,
temperature=temperature,
control_step=control_step,
time_constant=time_constant,
)
self._kwargs = get_arguments(locals(), kwargs)
self.scale_min = scale_min
self.scale_max = scale_max
self.ratio = self.control_step * self.time_step / self.time_constant
[docs] def set_time_step(self, dt):
r"""
Set simulation time step
Args:
dt (float): Simulation time step
"""
self.time_step = dt
self.ratio = self.control_step * self.time_step / self.time_constant
return self
def construct(self,
coordinate: Tensor,
velocity: Tensor,
force: Tensor,
energy: Tensor,
kinetics: Tensor,
virial: Tensor = None,
pbc_box: Tensor = None,
step: int = 0,
) -> Tuple[Tensor, Tensor, Tensor, Tensor, Tensor, Tensor, Tensor]:
r"""
Control the temperature of the simulation system using Berendsen (weak coupling) thermostat.
Args:
coordinate (Tensor): Tensor of shape :math:`(B, A, D)`. Data type is float.
velocity (Tensor): Tensor of shape :math:`(B, A, D)`. Data type is float.
force (Tensor): Tensor of shape :math:`(B, A, D)`. Data type is float.
energy (Tensor): Tensor of shape :math:`(B, 1)`. Data type is float.
kinetics (Tensor): Tensor of shape :math:`(B, D)`. Data type is float.
virial (Tensor): Tensor of shape :math:`(B, D)`. Data type is float.
pbc_box (Tensor): Tensor of shape :math:`(B, D)`. Data type is float.
step (int): Simulation step. Default: ``0``.
Returns:
- **coordinate** (Tensor) - Tensor of shape :math:`(B, A, D)`. Data type is float.
- **velocity** (Tensor) - Tensor of shape :math:`(B, A, D)`. Data type is float.
- **force** (Tensor) - Tensor of shape :math:`(B, A, D)`. Data type is float.
- **energy** (Tensor) - Tensor of shape :math:`(B, 1)`. Data type is float.
- **kinetics** (Tensor) - Tensor of shape :math:`(B, D)`. Data type is float.
- **virial** (Tensor) - Tensor of shape :math:`(B, D)`. Data type is float.
- **pbc_box** (Tensor) - Tensor of shape :math:`(B, D)`. Data type is float.
Note:
:math:`B` is the number of walkers in simulation.
:math:`A` is the number of atoms.
:math:`D` is the spatial dimension of the simulation system. Usually is 3.
"""
if self.control_step == 1 or step % self.control_step == 0:
scale = self.velocity_scale(kinetics, self.get_ref_kinetics(), self.ratio)
scale = ops.clip_by_value(scale, self.scale_min, self.scale_max)
velocity *= scale
return coordinate, velocity, force, energy, kinetics, virial, pbc_box