Tropospheric Chemistry Modelling Group

EVAPORATION (Estimation of VApor Pressure of ORganics, Accounting for Temperature, IntramOlecular and Neighbour effects) is, like the CM model, a model to estimate the vapor pressure of organic molecules, but more detailed.

Molecules residing in secondary organic aerosol are typically polyfunctional. The simple scheme of group-additivity in log(p) used in the CM model fails to some extent especially for hydrogen-bonding groups (hydroxy, acid,...). Also, in recent years, new data on polyfunctional molecules -especially functionalized diacids- became available (e.g. Soonsin et al., Atmos. Chem. Phys. 2010 , Booth et al., Atmos. Chem. Phys. 2010) , although it must be noted that there exists considerably uncertainty on these data, as measurement of low vapor pressures is technically challenging.

The main improvements of EVAPORATION are that it is based on a considerably larger data base, that it includes neighbour interactions between functional groups and that it goes beyond the simple scheme of group-additivity in log(p).

The deviation of additivity for e.g. diacids and diols can be thermodynamically rationalized. For functionalized diacids an extra ad-hoc modification was introduced. However, more recent data of Huisman et al., (Atmos. Chem. Phys. Discuss. 2013) is in clear disagreement with this modification, therefore the user can choose to turn it off.



Compernolle, S., K. Ceulemans, and J.-F. Müller, EVAPORATION: a new vapor pressure estimation method for organic molecules including non-additivity and intramolecular interactions, Atmos. Chem. Phys., 19431-9450, 2011. [abstract][pdf]