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):
 UCRLJRNL227406
TRN: US200824%%75
 DOE Contract Number:
 W7405ENG48
 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, ZepedaRuiz, 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, ZepedaRuiz, L A, Gee, R H, & Burnham, A. Sublimation rate of molecular crystals  role of internal degrees of freedom. United States.
Maiti, A, ZepedaRuiz, 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 ZepedaRuiz, 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}
}

The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2trichloro1,2,2trifluoroethane (CCl{sub 2}F–CClF{sub 2}, F113) have been measured under equilibrium pressure within the lowtemperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2tetrachloro1,2difluoroethane (CCl{sub 2}F–CCl{sub 2}F, F112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsiblemore »

Molecular modeling of micelle formation and solubilization in block copolymer micelles. 2. Lattice theory for monomers with internal degrees of freedom
A selfconsistent meanfield lattice theory of the micellization and solubilization properties of poly(ethylene oxide)poly(propylene oxide) block copolymers is described. The polymer segments are allowed to assume both polar and nonpolar conformations (corresponding to the gauche and trans rotations of the CC and CO bonds), which permits the dependence of the segmentsegment interactions on temperature and composition to be accounted for in a physically realistic manner. The phase diagrams of poly(ethylene oxide) and poly(propylene oxide) in water, both of which exhibit lower critical solution temperatures, can be reproduced semiquantitatively. The predictions of the theory compare favorably with published light scattering resultsmore » 
Boundary conditions for fluids with internal orientational degrees of freedom: Apparent velocity slip associated with the molecular alignment
Boundary effects are investigated for fluids with internal orientational degrees of freedom such as molecular liquids, thermotropic and lyotropic liquid crystals, and polymeric fluids. The orientational degrees of freedom are described by the second rank alignment tensor which is related to the birefringence. We use a standard model to describe the orientational dynamics in the presence of flow, the momentum balance equations, and a constitutive law for the pressure tensor to describe our system. In the spirit of irreversible thermodynamics, boundary conditions are formulated for the mechanical slip velocity and the flux of the alignment. They are set up suchmore » 
Characteristics of energy exchange between inter and intramolecular degrees of freedom in crystalline 1,3,5triamino2,4,6trinitrobenzene (TATB) with implications for coarsegrained simulations of shock waves in polyatomic molecular crystals
In this report, we characterize the kinetics and dynamics of energy exchange between intramolecular and intermolecular degrees of freedom (DoF) in crystalline 1,3,5triamino2,4,6trinitrobenzene (TATB). Allatom molecular dynamics (MD) simulations are used to obtain predictions for relaxation from certain limiting initial distributions of energy between the intra and intermolecular DoF. The results are used to parameterize a coarsegrained Dissipative Particle Dynamics at constant Energy (DPDE) model for TATB. Each TATB molecule in the DPDE model is represented as an allatom, rigidmolecule mesoparticle, with explicit external (molecular translational and rotational) DoF and coarsegrained implicit internal (vibrational) DoF. In addition to conserving linearmore »