Equations of State 

VESIcal implements multiple equations of state that are used in the VESIcal submodels, which are accessible to the user. This modular implementation of the components of the submodels allows them to be adjusted or even hybridized.

Ideal Gas Law 

Description	Phase	Function
Returns the fugacity of an ideal gas, i.e., the partial pressure.	H2O, CO2	`fugacity_idealgas()`

Kerrick and Jacobs (1981)

Description	Phase	Function
Implementation of the Kerrick and Jacobs (1981) EOS for mixed fluids.	H2O, CO2	`fugacity_KJ81_h2o()`, `fugacity_KJ81_co2()`

Zhang and Duan (2009)

Description	Phase	Function
Implementation of the Zhang and Duan (2009) fugacity model for pure CO2 fluids.	CO2	`fugacity_ZD09_co2()`

Modified Redlich Kwong 

Description	Phase	Function
Fugacity model as used by VolatileCalc. Python implementation by D. J Rasmussen (github.com/DJRgeoscience/VolatileCalcForPython), based on VB code by Newman & Lowenstern (2002).	H2O, CO2	`fugacity_MRK_h2o()`, `fugacity_MRK_co2()`
Modified Redlich Kwong by Holloway and Blank (1994)	H2O, CO2	`fugacity_HB_h2o()`, `fugacity_HB_co2()`
Implementation of the Modified Redlich Kwong presented in Holloway and Blank (1994) Reviews in Mineralogy and Geochemistry vol. 30. Originally written in Quickbasic. CO2 calculations translated to Matlab by Chelsea Allison and translated to python by K. Iacovino for VESIcal. H2O calculations translated to VisualBasic by Gordon M. Moore and translated to python by K. Iacovino for VESIcal.	CO2	`fugacity_HollowayBlank()`

Redlich Kwong 

Description	Phase	Function
Implementation of the Redlich Kwong EoS by Patrick J. Barrie 30 October 2003. Code derived from http://people.ds.cam.ac.uk/pjb10/thermo/pure.html	H2O, CO2, mixed H2O-CO2	`fugacity_RK_h2o()`, `fugacity_RK_co2()`, `fugacity_RedlichKwong`

Example Use Cases 

Model hybridization
Custom Equations of State
Extracting thermodynamic values from a VESIcal calculation