# Empirical Models¶

Empirical models predict thermodynamic properties of species using simple polynomials. These can be evaluated more quickly than statistical mechanical equations and tend to be used by kinetic modeling software.

When fitting an empirical relationship, be mindful that the resulting polynomial will have the same reference state as the original data. Databases like the NIST Chemistry WebBook and Burcat tend to use the standard reference (i.e. pure elements in their natural state at 1 atm have a standard enthalpy of formation of 0). However, data from DFT software (and DFT-based references) may use different references. See Referencing for more information.

## Parent Class¶

 EmpiricalBase

## Nasa¶

 nasa.Nasa nasa.SingleNasa9 nasa.Nasa9

## Shomate¶

 shomate.Shomate

## Referencing¶

Referencing is used to bridge the gap between ab-initio code reference states and the standard state reference. See Referencing for more information.

 references.Reference references.References

## Misc.¶

Miscellaneous models associated with the empirical models are located here.

 GasPressureAdj