pmutt.statmech.rot.RigidRotor

class pmutt.statmech.rot.RigidRotor(symmetrynumber, rot_temperatures=None, geometry=None, atoms=None, degree_tol=5.0)

Bases: _ModelBase

Rotational mode using the rigid rotor assumption. Equations sourced from:

Sandler, S. I. An Introduction to Applied Statistical Thermodynamics; John Wiley & Sons, 2010.

symmetrynumber

Symmetry number of molecule. If a string is inputted, it represents the point group. Supported options are shown below.

Point group	symmetry number
C1	1
Cs	1
C2	2
C2v	2
C3v	3
Cinfv	1
D2h	4
D3h	6
D5h	10
Dinfh	2
D3d	6
Td	12
Oh	24

See DOI for more details: 10.1007/s00214-007-0328-0

Type:: float or str

rot_temperatures

Rotational temperatures in K

Type:: list of float, optional

geometry

Geometry of molecule. Accepted options are:

monatomic
linear
nonlinear

Type:: str

atoms

An atoms object can be used to calculate rot_temperatures and guess geometry

Type:: ase.Atoms object, optional

degree_tol

Degree tolerance to estimate geometry. Only required if estimating geometry or rot_temperatures

Type:: float

__init__(symmetrynumber, rot_temperatures=None, geometry=None, atoms=None, degree_tol=5.0)

Methods

`__init__`(symmetrynumber[, rot_temperatures, ...])
`from_dict`(json_obj)	Recreate an object from the JSON representation.
`get_Cp`(units, **kwargs)	Calculate the heat capacity (constant P)
`get_CpoR`()	Calculates the dimensionless heat capacity at constant pressure
`get_Cv`(units, **kwargs)	Calculate the heat capacity (constant V)
`get_CvoR`()	Calculates the dimensionless heat capacity at constant volume
`get_F`(units[, T])	Calculate the Helmholtz energy
`get_FoRT`(T)	Calculates the dimensionless Helmholtz energy
`get_G`(units[, T])	Calculate the Gibbs energy
`get_GoRT`(T)	Calculates the dimensionless Gibbs energy
`get_H`(units[, T])	Calculate the enthalpy
`get_HoRT`()	Calculates the dimensionless enthalpy
`get_S`(units, **kwargs)	Calculate the entropy
`get_SoR`(T)	Calculates the dimensionless entropy
`get_U`(units[, T])	Calculate the internal energy
`get_UoRT`()	Calculates the dimensionless internal energy
`get_q`(T)	Calculates the partition function
`to_dict`()	Represents object as dictionary with JSON-accepted datatypes

classmethod from_dict(json_obj)

Recreate an object from the JSON representation.

Parameters:: json_obj (dict) – JSON representation
Returns:: Obj
Return type:: Appropriate object

get_Cp(units, **kwargs)

Calculate the heat capacity (constant P)

Parameters:

units (str) – Units as string. See R() for accepted units.
kwargs (keyword arguments) – Parameters needed by get_CpoR

Returns:

Cp – Heat capacity (constant P) in appropriate units

Return type:

float

get_CpoR()

Calculates the dimensionless heat capacity at constant pressure

\(\frac{C_P^{rot}}{R}=\frac{C_V^{rot}}{R}\)

Returns:: CpoR_rot – Rotational dimensionless heat capacity at constant pressure
Return type:: float

get_Cv(units, **kwargs)

Calculate the heat capacity (constant V)

Parameters:

units (str) – Units as string. See R() for accepted units.
kwargs (keyword arguments) – Parameters needed by get_CvoR

Returns:

Cv – Heat capacity (constant V) in appropriate units

Return type:

float

get_CvoR()

Calculates the dimensionless heat capacity at constant volume

\(\frac{C_V^{rot}}{R}=0\) if monatomic

\(\frac{C_V^{rot}}{R}=1\) if linear

\(\frac{C_V^{rot}}{R}=1.5\) if nonlinear

Returns:: CvoR_rot – Rotational dimensionless heat capacity at constant volume
Return type:: float

get_F(units, T=298.15, **kwargs)

Calculate the Helmholtz energy

Parameters:

units (str) – Units as string. See R() for accepted units but omit the ‘/K’ (e.g. J/mol).
T (float, optional) – Temperature in K. Default is 298.15 K
kwargs (keyword arguments) – Parameters needed by get_FoRT

Returns:

F – Hemholtz energy in appropriate units

Return type:

float

get_FoRT(T)

Calculates the dimensionless Helmholtz energy

\(\frac{A^{rot}}{RT}=\frac{U^{rot}}{RT}-\frac{S^{rot}}{R}\)

Parameters:: T (float) – Temperature in K
Returns:: FoRT_rot – Rotational dimensionless Helmholtz energy
Return type:: float

get_G(units, T=298.15, **kwargs)

Calculate the Gibbs energy

Parameters:

units (str) – Units as string. See R() for accepted units but omit the ‘/K’ (e.g. J/mol).
T (float, optional) – Temperature in K. Default is 298.15 K
kwargs (keyword arguments) – Parameters needed by get_GoRT

Returns:

G – Gibbs energy in appropriate units

Return type:

float

get_GoRT(T)

Calculates the dimensionless Gibbs energy

\(\frac{G^{rot}}{RT}=\frac{H^{rot}}{RT}-\frac{S^{rot}}{R}\)

Parameters:: T (float) – Temperature in K
Returns:: GoRT_rot – Rotational dimensionless Gibbs energy
Return type:: float

get_H(units, T=298.15, **kwargs)

Calculate the enthalpy

Parameters:

units (str) – Units as string. See R() for accepted units but omit the ‘/K’ (e.g. J/mol).
T (float, optional) – Temperature in K. Default is 298.15 K
kwargs (keyword arguments) – Parameters needed by get_HoRT

Returns:

H – Enthalpy in appropriate units

Return type:

float

get_HoRT()

Calculates the dimensionless enthalpy

\(\frac{U^{rot}}{RT}=\frac{H^{rot}}{RT}\)

Returns:: HoRT_rot – Rotational dimensionless enthalpy
Return type:: float

get_S(units, **kwargs)

Calculate the entropy

Parameters:

units (str) – Units as string. See R() for accepted units.
kwargs (keyword arguments) – Parameters needed by get_SoR

Returns:

S – Entropy in appropriate units

Return type:

float

get_SoR(T)

Calculates the dimensionless entropy

\(\frac{S^{rot}}{R}=0\) if monatomic

\(\frac{S}{R}=\log(\frac{T}{\sigma}\prod_i \frac{1}{ \Theta_{R,i}})+1\) if linear

\(\frac{S^{rot}}{R}=\log\bigg(\frac{\sqrt\pi }{\sigma} \prod_i{(\frac{T^3}{\Theta_{R,i}})^\frac{1}{2}}\bigg)+1.5\) if nonlinear

Parameters:: T (float) – Temperature in K
Returns:: SoR_rot – Rotational dimensionless entropy
Return type:: float

get_U(units, T=298.15, **kwargs)

Calculate the internal energy

Parameters:

units (str) – Units as string. See R() for accepted units but omit the ‘/K’ (e.g. J/mol).
T (float, optional) – Temperature in K. Default is 298.15 K
kwargs (keyword arguments) – Parameters needed by get_UoRT

Returns:

U – Internal energy in appropriate units

Return type:

float

get_UoRT()

Calculates the dimensionless internal energy

\(\frac{U^{rot}}{RT}=0\) if monatomic

\(\frac{U^{rot}}{RT}=1\) if linear

\(\frac{U^{rot}}{RT}=1.5\) if nonlinear

Returns:: UoRT_rot – Rotational dimensionless internal energy
Return type:: float

get_q(T)

Calculates the partition function

\(q^{rot}=0\) if monatomic

\(q^{rot}=\frac{T}{\sigma}\prod_i\frac{1}{\Theta_R}\) if linear

\(q^{rot}=\frac{\sqrt{\pi}}{\sigma}(T^3\prod_i\frac{1}{ \Theta_{Ri}})^\frac{1}{2}\) if nonlinear

Parameters:: T (float) – Temperature in K
Returns:: q_rot – Rotational partition function
Return type:: float

to_dict()

Represents object as dictionary with JSON-accepted datatypes

Returns:: obj_dict
Return type:: dict