Eigenstates of Thiophosgene Near the Dissociation Threshold: Deviations From Ergodicity

2016

J. Phys. Chem. Lett.

The nature and rate of thermal transport through molecular junctions depend on the length over which thermalization occurs. For junctions formed by alkane chains, in which thermalization occurs only slowly, measurements reveal that thermal resistance is controlled by bonding with the substrates, whereas fluorination can introduce thermal resistance within the molecules themselves, although the mechanism remains unclear. Here we present results of quantum-mechanical calculations of elastic and inelastic scattering rates, the length over which thermalization occurs, and thermal conductance in alkane and perfluoroalkane junctions. The contribution to thermalization of quantum effects that give rise to many-body localization (MBL) in isolated molecules is examined. While MBL does not occur due to dephasing, thermalization is typically too slow to establish local temperature if the same molecule in isolation exhibits MBL. The results indicate limitations on the applicability of classical molecular simulations in modeling thermal transport in molecular junctions.

mentioning

confidence: 63%

Thermalization and Thermal Transport in Molecules

2016

J. Phys. Chem. Lett.

“…Nevertheless, we expect that vibrational energy transport dynamics in molecules may be diffusive even if the limit of strong mixing modeled by the GOE is not yet reached. This expectation is based on experience with local random matrix theory (LRMT) [19], which captures the diffusion in vibrational state space of a molecule even when the corresponding classical dynamics in phase space is not fully chaotic [66][67][68][69][70]. Similarly, we expect vibrational energy propagated by eigenmodes of the Hessian matrix may well exhibit diffusive dynamics even if the statistical properties of the eigenmodes do not coincide with those of the GOE.…”

Section: Discussionmentioning

confidence: 99%

Vibrational energy transport in molecules and the statistical properties of vibrational modes

2017

Chemical Physics

Statistical properties of the eigenmodes computed for two molecules, dodecane and perfluorododecane, are examined and compared with predictions of random matrix theory. The eigenmode statistics of the heat carrying modes of perfluorododecane correspond to Porter-Thomas statistics, whereas those for dodecane do not. Vibrational energy transport in the two molecules is also computed and found to be diffusive in perfluorododecane but not in dodecane, consistent with recent experiments. The correspondence between eigenmode statistics and vibrational energy transport dynamics in molecules as well as thermalization in molecules are discussed.

“…Indeed, spectra of large molecules are determined by coupling involving many such tiers of states. − With many tiers emerges the possibility of localization in the vibrational state space, , as has been observed for molecules where the total density of states is quite large . The resulting long-lived vibrations can be found at energies sufficient for chemical reactions and mediate chemical reaction kinetics involving sizable molecules in gas and condensed phases and in biomolecules. − Similarly, tier models have provided insights into the role of resonances and anharmonicity in vibrational energy relaxation and thermalization in molecules at interfaces between two materials and thermal conduction through the interface. − Some of that work has examined the possibility of energy rectification in molecules, where there is a propensity for energy to flow in molecules preferentially from one chemical group to another in condensed phase or at an interface. − …”

Section: Introductionmentioning

confidence: 98%

Vibrational States and Nitrile Lifetimes of Cyanophenylalanine Isotopomers in Solution

2018

J. Phys. Chem. A

Nitrile lifetimes and the structure of the vibrational state space of four isotopomers of cyanophenylalanine in solution are calculated. While the frequency of the nitrile of the four isotopomers decreases in the order CN, CN, CN, and CN, the lifetime varies nonmonotonically with the change in frequency. The vibrational properties of the molecules that control the lifetime are examined. The specific resonances that contribute to the lifetime are tuned by isotopic substitution, and the magnitudes of the anharmonic constants involved in the coupling of vibrations that mediate the lifetime of the nitrile vary with CN mass. The nature of the modes coupled to the nitrile varies, as the frequency of the nitrile changes with isotopic substitution. For some CN frequencies the modes coupled to the CN are rather localized to the ring, while at other frequencies the modes coupled to the CN are more delocalized. Comparison of the calculated frequencies and lifetimes with recent experimental measurements on these molecules is discussed.