rmgpy.thermo.NASAPolynomial¶
- class rmgpy.thermo.NASAPolynomial(coeffs=None, Tmin=None, Tmax=None, E0=None, label='', comment='')¶
A heat capacity model based on the NASA polynomial. Both the seven-coefficient and nine-coefficient variations are supported. The attributes are:
Attribute
Description
coeffs
The seven or nine NASA polynomial coefficients
Tmin
The minimum temperature in K at which the model is valid, or zero if unknown or undefined
Tmax
The maximum temperature in K at which the model is valid, or zero if unknown or undefined
E0
The energy at zero Kelvin (including zero point energy)
comment
Information about the model (e.g. its source)
The NASA polynomial is another representation of the heat capacity, enthalpy, and entropy using seven or nine coefficients \(\mathbf{a} = \left[a_{-2}\ a_{-1}\ a_0\ a_1\ a_2\ a_3\ a_4\ a_5\ a_6 \right]\). The relevant thermodynamic parameters are evaluated via the expressions
\[\frac{C_\mathrm{p}(T)}{R} = a_{-2} T^{-2} + a_{-1} T^{-1} + a_0 + a_1 T + a_2 T^2 + a_3 T^3 + a_4 T^4\]\[\frac{H(T)}{RT} = - a_{-2} T^{-2} + a_{-1} T^{-1} \ln T + a_0 + \frac{1}{2} a_1 T + \frac{1}{3} a_2 T^2 + \frac{1}{4} a_3 T^3 + \frac{1}{5} a_4 T^4 + \frac{a_5}{T}\]\[\frac{S(T)}{R} = -\frac{1}{2} a_{-2} T^{-2} - a_{-1} T^{-1} + a_0 \ln T + a_1 T + \frac{1}{2} a_2 T^2 + \frac{1}{3} a_3 T^3 + \frac{1}{4} a_4 T^4 + a_6\]In the seven-coefficient version, \(a_{-2} = a_{-1} = 0\).
As simple polynomial expressions, the NASA polynomial is faster to evaluate when compared to the Wilhoit model; however, it does not have the nice physical behavior of the Wilhoit representation. Often multiple NASA polynomials are used to accurately represent the thermodynamics of a system over a wide temperature range; the
NASA
class is available for this purpose.- Cp0¶
The heat capacity at zero temperature.
- CpInf¶
The heat capacity at infinite temperature.
- E0¶
The ground state energy (J/mol) at zero Kelvin, including zero point energy, or
None
if not yet specified.
- Tmax¶
The maximum temperature at which the model is valid, or
None
if not defined.
- Tmin¶
The minimum temperature at which the model is valid, or
None
if not defined.
- as_dict(self) dict ¶
- c0¶
‘double’
- Type:
c0
- c1¶
‘double’
- Type:
c1
- c2¶
‘double’
- Type:
c2
- c3¶
‘double’
- Type:
c3
- c4¶
‘double’
- Type:
c4
- c5¶
‘double’
- Type:
c5
- c6¶
‘double’
- Type:
c6
- change_base_enthalpy(self, double deltaH)¶
Add deltaH in J/mol to the base enthalpy of formation H298.
- change_base_entropy(self, double deltaS)¶
Add deltaS in J/molK to the base entropy of formation S298.
- cm1¶
‘double’
- Type:
cm1
- cm2¶
‘double’
- Type:
cm2
- coeffs¶
The set of seven or nine NASA polynomial coefficients.
- comment¶
unicode
- Type:
comment
- discrepancy(self, HeatCapacityModel other) double ¶
Return some measure of how dissimilar self is from other.
The measure is arbitrary, but hopefully useful for sorting purposes. Discrepancy of 0 means they are identical
- get_enthalpy(self, double T) double ¶
Return the enthalpy in J/mol at the specified temperature T in K.
- get_entropy(self, double T) double ¶
Return the entropy in J/mol*K at the specified temperature T in K.
- get_free_energy(self, double T) double ¶
Return the Gibbs free energy in J/mol at the specified temperature T in K.
- get_heat_capacity(self, double T) double ¶
Return the constant-pressure heat capacity in J/mol*K at the specified temperature T in K.
- is_identical_to(self, HeatCapacityModel other) bool ¶
Returns
True
if self and other report very similar thermo values for heat capacity, enthalpy, entropy, and free energy over a wide range of temperatures, orFalse
otherwise.
- is_similar_to(self, HeatCapacityModel other) bool ¶
Returns
True
if self and other report similar thermo values for heat capacity, enthalpy, entropy, and free energy over a wide range of temperatures, orFalse
otherwise.
- is_temperature_valid(self, double T) bool ¶
Return
True
if the temperature T in K is within the valid temperature range of the thermodynamic data, orFalse
if not. If the minimum and maximum temperature are not defined,True
is returned.
- label¶
unicode
- Type:
label
- make_object(self, dict data, dict class_dict)¶
A helper function for constructing objects from a dictionary (used when loading YAML files)
- Parameters:
data (dict) – The dictionary representation of the object
class_dict (dict) – A mapping of class names to the classes themselves
- Returns:
None