Vapor Pressure and Sublimation Rate of Molecular Crystals: Role of Internal Degrees of Freedom

Authors:
Publisher website
Google Scholar
Abstract
It is a common practice to approximate the desorption rate of atoms from crystal surfaces with an expression of the form νeff exp(−ΔE/kBT), where ΔE is an activation barrier to desorb and νeff is an effective vibrational frequency ∼1012 s-1. For molecular solids, however, such an approximation can lead to a many orders of magnitude underestimation of vapor pressure and sublimation rates due to neglected contributions from molecular internal degrees of freedom. Here, we develop a simple working formula that yields good estimates for a general molecular (or atomic) solid and illustrate the approach by computing equilibrium vapor pressure of three different molecular solids and an atomic solid, as well as the desorption rate of a foreign (inhibitor) molecule from the surface of a molecular solid.

This publication has 17 references indexed in Scilit: