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Title: Sublimation rate of molecular crystals - role of internal degrees of freedom

Abstract

It is a common practice to estimate site desorption rate from crystal surfaces with an Arrhenius expression of the form v{sub eff} exp(-{Delta}E/k{sub B}T), where {Delta}E is an activation barrier to desorb and v{sub eff} is an effective vibrational frequency {approx} 10{sup 12} sec{sup -1}. However, such a formula can lead to several to many orders of magnitude underestimation of sublimation rates in molecular crystals due to internal degrees of freedom. We carry out a quantitative comparison of two energetic molecular crystals with crystals of smaller entities like ice and Argon (solid) and uncover the errors involved as a function of molecule size. In the process, we also develop a formal definition of v{sub eff} and an accurate working expression for equilibrium vapor pressure.

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940512
Report Number(s):
UCRL-JRNL-227406
TRN: US200824%%75
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry B, vol. 111, N/A, November 30, 2007, pp. 14290; Journal Volume: 111
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ARGON; DEGREES OF FREEDOM; DESORPTION; MOLECULAR CRYSTALS; SUBLIMATION; VAPOR PRESSURE

Citation Formats

Maiti, A, Zepeda-Ruiz, L A, Gee, R H, and Burnham, A. Sublimation rate of molecular crystals - role of internal degrees of freedom. United States: N. p., 2007. Web.
Maiti, A, Zepeda-Ruiz, L A, Gee, R H, & Burnham, A. Sublimation rate of molecular crystals - role of internal degrees of freedom. United States.
Maiti, A, Zepeda-Ruiz, L A, Gee, R H, and Burnham, A. Fri . "Sublimation rate of molecular crystals - role of internal degrees of freedom". United States. doi:. https://www.osti.gov/servlets/purl/940512.
@article{osti_940512,
title = {Sublimation rate of molecular crystals - role of internal degrees of freedom},
author = {Maiti, A and Zepeda-Ruiz, L A and Gee, R H and Burnham, A},
abstractNote = {It is a common practice to estimate site desorption rate from crystal surfaces with an Arrhenius expression of the form v{sub eff} exp(-{Delta}E/k{sub B}T), where {Delta}E is an activation barrier to desorb and v{sub eff} is an effective vibrational frequency {approx} 10{sup 12} sec{sup -1}. However, such a formula can lead to several to many orders of magnitude underestimation of sublimation rates in molecular crystals due to internal degrees of freedom. We carry out a quantitative comparison of two energetic molecular crystals with crystals of smaller entities like ice and Argon (solid) and uncover the errors involved as a function of molecule size. In the process, we also develop a formal definition of v{sub eff} and an accurate working expression for equilibrium vapor pressure.},
doi = {},
journal = {Journal of Physical Chemistry B, vol. 111, N/A, November 30, 2007, pp. 14290},
number = ,
volume = 111,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}
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