Ideal gas model

Ideal gas model#

Thermochemistry calculation from frequencies and coordinates. Copied from otherm (duartegroup/otherm) 16/05/2021. See autode/common/thermochemistry.pdf for mathematical background

All calculations performed in SI units, for simplicity.

class autode.thermochemistry.igm.LFMethod(value)#

Method to treat low-frequency modes

See also

autode.thermochemistry.igm.calculate_thermo_cont for citations for the different methods.

grimme = 2#
igm = 0#
minenkov = 3#
truhlar = 1#
class autode.thermochemistry.igm.SIConstants#

Constants in SI (International System of Units) units

c = 299792458#
h = 6.62607004e-34#
k_b = 1.38064852e-23#
autode.thermochemistry.igm.calculate_thermo_cont(species: Species, temp: ~autode.values.Temperature = Temperature(298.15 kelvin), **kwargs: ~typing.Any)#

Calculate and set the thermochemical contributions (Enthalpic, Free Energy) of a species using a variant of the ideal gas model (RRHO). Appends energies to species.energies. Default methods are set in autode.config.Config. See references:

[1] Chem. Eur. J. 2012, 18, 9955

[2] J. Phys. Chem. B, 2011, 115, 14556

[3] J. Comput. Chem., 2023, 44, 1807

Parameters:

temp (autode.values.Temperature) – Temperature in K. Default: 298.15 K

Keyword Arguments:

  • lfm_method (str | LFMethod) – Method used to calculate the molecular entropy by treating the low frequency modes. One of: {‘igm’, ‘truhlar’, ‘grimme’, ‘minenkov’}. Default: Config.lfm_method

  • ss (str) – Standard state at which the molecular entropy is calculated. Should be 1M for a solution phase molecule and 1 atm for a molecule in the gas phase. Default: Config.standard_state

  • shift (float | Frequency) – Frequency parameters for Truhlar’s method, if float then assumed cm-1 units. Only used if method=’truhlar’. Default: Config.vib_freq_shift

  • w0 (float | Frequency) – ω0 parameter, if float then assumed cm-1 units Default: Config.grimme_w0

  • alpha (int | float) – α parameter in Grimme’s qRRHO method. Default: Config.grimme_w0

  • sn (int) – The symmetry number, if not present then will default to species.sn

Raises:

(KeyError | ValueError) – If frequencies are not defined

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