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Research & Reviews: Journal of Material Sciences | ISSN: 2321-6212 | Volume 6
Theoretical, Materials and Condensed Matter Physics
5
th
International Conference on
November 26-28, 2018 | Los Angeles, USA
Estimating vibrational lifetime and boundary conductance
Hari Datt Pandey
University of California Riverside, USA
E
stimating vibrational signatures of a large molecular system is even tricky because of overlapping frequencies. Therefore,
the vibrational probes are used to distinguish the vibrational signatures in the IR experiments. The underlying anharmonic
interactions and prevailing resonances within the energy space dictate the vibrational lifetime, localization, participation, and
energy flow pathway. These processes can be estimated from the quasiharmonic approximation accounting the intramolecular
vibrational energy redistribution (IVR). The IVR process is irreversible and collisionless within the specified timescale of
interest. We computed the IVR properties of liquid alkylbenzene systems by solving the vibrational Hamiltonian with the
potential up to cubic or quartic anharmonic terms deriving the self-consistent system of nonlinear equation
1-3
. Only addressing
the modes of interest and solving iteratively, the vibrational properties can be computed. Later we estimated the vibrational
lifetime of the isotopically substituted nitrile probe, cyanophenylalanine
4-5
. The frequency of the nitrile of the four isotopomers
decreases in the order
12
C
14
N,
12
C
15
N,
13
C
14
N, and
13
C
15
N, whereas the corresponding lifetime varies nonmonotonically with
the change in frequency. The estimated lifetime first two C-N stretches are within 15% of the experimentally measured value
4.0, 2.4, 2.0, and 3.7 ps respectively and the other two are off by a factor of 2.
4-5
In the unsubstituted,
12
C
14
N, the coupled state
are nonresonant at the level of cubic anharmonic interaction, whereas in other cases the energy flow is via the resonantly
coupled pathway. The lifetime of
13
C
15
N is slower contradicting the general convention that closer the resonance, faster the
energy flow. We found that for some resonantly coupled modes to the CN are localized to the ring, while at other they are more
delocalized. The resonantly coupled states are localized bright states and preferably is the reason behind the longer lifetime
of the isotopically substituted case
4
. The IVR estimation method is also useful to determine the many-body localization-
thermalization transition to estimate the boundary conductance. We have estimated the boundary conductance of various
metal-alkane/perfluoroalkane-sapphier, metal-polyethylene glycol (PEG) oligomer junctions, and the results also agree with
the experiments
6-11
.
Biography
Hari Datt Pandey has completed his PhD in 2018 from University of Nevada Reno, USA and currently a Postdoc at University of California Riverside. He has
published more than ten publications in his graduate study. His was involved in research of vibrational energy flow, and boundary conductance in the field of
condensed matter physics. He was also involved in the dynamics of soft matters and currently participating in a conformational study of the protein, drug designing,
and binding kinetics.
pandey.dhkn@gmail.comHari Datt Pandey, Res. Rev. J Mat. Sci. 2018, Volume 6
DOI: 10.4172/2321-6212-C10-041