cctk.VibrationalMode

class cctk.VibrationalMode(frequency, force_constant, reduced_mass, intensity, displacements)

Bases: object

Most code adapted from jprogdyn. Displacements will be very low accuracy unless freq=hpmodes is enabled.

Values from Gaussian, for now: see https://gaussian.com/vib/.

frequency

frequency, in cm-1

Type:

float

force_constant

force constant, in kcal/mol per Å

Type:

float

reduced_mass

mass, in amus

Type:

float

intensity

IR intensity

Type:

float

displacements

atom displacements

Type:

cctk.OneIndexedArray

velocities

atom velocities

Type:

cctk.OneIndexedArray

__init__(frequency, force_constant, reduced_mass, intensity, displacements)

Methods

__init__(frequency, force_constant, ...)
choose_level([temperature])
classical_distribution_value(x)	Returns the value of the classical distribution at the specified x value.
classical_turning_point([energy])	Returns the maximum allowed shift based on modelling the mode as a classical harmonic oscillator (e.g. the point where potential energy is maximum).
energy([level])	Calculate energy as a function of level.
from_string()
quantum_distribution_max([level, num_pts])	Returns the maximum value of psi**2 for the quantum harmonic oscillator at a given level.
quantum_distribution_value(x[, level])	Calculate psi**2 for quantum harmonic oscillator for a given shift in Å.
random_displacement([energy, level, method, ...])	param energy: energy of mode (for classical case)
to_string()

choose_level(temperature=298)

classical_distribution_value(x)

Returns the value of the classical distribution at the specified x value.

classical_turning_point(energy=None)

Returns the maximum allowed shift based on modelling the mode as a classical harmonic oscillator (e.g. the point where potential energy is maximum).

Parameters:

• energy (float) – energy of mode

• level (int) – level to compute energy for quantum harmonic oscillator

energy(level=0)

Calculate energy as a function of level. By default returns zero-point energy (level = 0).

Parameters:

level (int) – which vibrational level the mode is in

Returns:

energy (kcal/mol)

from_string()

quantum_distribution_max(level=0, num_pts=10000.0)

Returns the maximum value of psi**2 for the quantum harmonic oscillator at a given level.

quantum_distribution_value(x, level=0)

Calculate psi**2 for quantum harmonic oscillator for a given shift in Å.

Parameters:

• x (float) – shift in Å

• level (int) – vibrational level

random_displacement(energy=None, level=0, method='quasiclassical', max_attempts=100000.0)

Parameters:

• energy (float) – energy of mode (for classical case)

• method (str) – “quasiclassical” or “classical”

• level (int) – which vibrational level

• max_attempts (int) – how many tries you get

Returns:

shift

to_string()