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"""LAMMPS has the options to use several internal units (which can be different
from the ones used in ase). Mapping is therefore necessary.
See: https://lammps.sandia.gov/doc/units.html
"""
from ase import units
from . import unitconvert_constants as u
# !TODO add reduced Lennard-Jones units?
# NOTE: We assume a three-dimensional simulation here!
DIM = 3.0
UNITSETS = {}
UNITSETS["ASE"] = dict(
mass=1.0 / units.kg,
distance=1.0 / units.m,
time=1.0 / units.second,
energy=1.0 / units.J,
velocity=units.second / units.m,
force=units.m / units.J,
pressure=1.0 / units.Pascal,
charge=1.0 / units.C,
)
UNITSETS["real"] = dict(
mass=u.gram_per_mole_si,
distance=u.angstrom_si,
time=u.femtosecond_si,
energy=u.kcal_per_mole_si,
velocity=u.angstrom_per_femtosecond_si,
force=u.kcal_per_mole_angstrom_si,
torque=u.kcal_per_mole_si,
temperature=u.kelvin_si,
pressure=u.atmosphere_si,
dynamic_viscosity=u.poise_si,
charge=u.e_si,
dipole=u.electron_angstrom_si,
electric_field=u.volt_per_angstrom_si,
density=u.gram_si / u.centimeter_si ** DIM,
)
UNITSETS["metal"] = dict(
mass=u.gram_per_mole_si,
distance=u.angstrom_si,
time=u.picosecond_si,
energy=u.ev_si,
velocity=u.angstrom_per_picosecond_si,
force=u.ev_per_angstrom_si,
torque=u.ev_si,
temperature=u.kelvin_si,
pressure=u.bar_si,
dynamic_viscosity=u.poise_si,
charge=u.e_si,
dipole=u.electron_angstrom_si,
electric_field=u.volt_per_angstrom_si,
density=u.gram_si / u.centimeter_si ** DIM,
)
UNITSETS["si"] = dict(
mass=u.kilogram_si,
distance=u.meter_si,
time=u.second_si,
energy=u.joule_si,
velocity=u.meter_per_second_si,
force=u.newton_si,
torque=u.joule_si,
temperature=u.kelvin_si,
pressure=u.pascal_si,
dynamic_viscosity=u.pascal_si * u.second_si,
charge=u.coulomb_si,
dipole=u.coulomb_meter_si,
electric_field=u.volt_per_meter_si,
density=u.kilogram_si / u.meter_si ** DIM,
)
UNITSETS["cgs"] = dict(
mass=u.gram_si,
distance=u.centimeter_si,
time=u.second_si,
energy=u.erg_si,
velocity=u.centimeter_per_second_si,
force=u.dyne_si,
torque=u.dyne_centimeter_si,
temperature=u.kelvin_si,
pressure=u.dyne_per_centimetersq_si, # or barye =u. 1.0e-6 bars
dynamic_viscosity=u.poise_si,
charge=u.statcoulomb_si, # or esu (4.8032044e-10 is a proton)
dipole=u.statcoulomb_centimeter_si, # =u. 10^18 debye,
electric_field=u.statvolt_per_centimeter_si, # or dyne / esu
density=u.gram_si / (u.centimeter_si ** DIM),
)
UNITSETS["electron"] = dict(
mass=u.amu_si,
distance=u.bohr_si,
time=u.femtosecond_si,
energy=u.hartree_si,
velocity=u.bohr_per_atu_si,
force=u.hartree_per_bohr_si,
temperature=u.kelvin_si,
pressure=u.pascal_si,
charge=u.e_si, # multiple of electron charge (1.0 is a proton)
dipole=u.debye_si,
electric_field=u.volt_per_centimeter_si,
)
UNITSETS["micro"] = dict(
mass=u.picogram_si,
distance=u.micrometer_si,
time=u.microsecond_si,
energy=u.picogram_micrometersq_per_microsecondsq_si,
velocity=u.micrometer_per_microsecond_si,
force=u.picogram_micrometer_per_microsecondsq_si,
torque=u.picogram_micrometersq_per_microsecondsq_si,
temperature=u.kelvin_si,
pressure=u.picogram_per_micrometer_microsecondsq_si,
dynamic_viscosity=u.picogram_per_micrometer_microsecond_si,
charge=u.picocoulomb_si, # (1.6021765e-7 is a proton),
dipole=u.picocoulomb_micrometer_si,
electric_field=u.volt_per_micrometer_si,
density=u.picogram_si / (u.micrometer_si) ** DIM,
)
UNITSETS["nano"] = dict(
mass=u.attogram_si,
distance=u.nanometer_si,
time=u.nanosecond_si,
energy=u.attogram_nanometersq_per_nanosecondsq_si,
velocity=u.nanometer_per_nanosecond_si,
force=u.attogram_nanometer_per_nanosecondsq_si,
torque=u.attogram_nanometersq_per_nanosecondsq_si,
temperature=u.kelvin_si,
pressure=u.attogram_per_nanometer_nanosecondsq_si,
dynamic_viscosity=u.attogram_per_nanometer_nanosecond_si,
charge=u.e_si, # multiple of electron charge (1.0 is a proton)
dipole=u.electron_nanometer_si,
electric_field=u.volt_si / u.nanometer_si,
density=u.attogram_si / u.nanometer_si ** DIM,
)
def convert(value, quantity, fromunits, tounits):
"""Convert units between LAMMPS and ASE.
:param value: converted value
:param quantity: mass, distance, time, energy, velocity, force, torque,
temperature, pressure, dynamic_viscosity, charge, dipole,
electric_field or density
:param fromunits: ASE, metal, real or other (see lammps docs).
:param tounits: ASE, metal, real or other
:returns: converted value
:rtype:
"""
return UNITSETS[fromunits][quantity] / UNITSETS[tounits][quantity] * value
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