scholarly journals Temperature dependence of the vibrational spectrum of porphycene: a qualitative failure of classical-nuclei molecular dynamics

2020 ◽  
Vol 221 ◽  
pp. 526-546 ◽  
Author(s):  
Yair Litman ◽  
Jörg Behler ◽  
Mariana Rossi
Keyword(s):  
Molecular Dynamics ◽  
Vibrational Spectrum ◽  
Temperature Dependence ◽  
High Frequency ◽  
Quantum Dynamics ◽  
Low Frequency ◽  
Blue Shift ◽  
Temperature Dependent ◽  
Vibrational Coupling ◽  
Thermally Activated

Approximate quantum dynamics succeed in predicting a temperature-dependent blue-shift of the high-frequency stretch bands that arise from vibrational coupling between low-frequency thermally activated modes and high-frequency quantized ones. Classical nuclei molecular dynamics fail and instead predict a red-shift.

Interpretation of temperature-dependent low frequency vibrational spectrum of solid-state benzoic acid dimer

2009 ◽  
Vol 479 (4-6) ◽  
pp. 211-217 ◽  
Author(s):  
Masae Takahashi ◽  
Yoshiyuki Kawazoe ◽  
Yoichi Ishikawa ◽  
Hiromasa Ito
Keyword(s):  
Solid State ◽  
Vibrational Spectrum ◽  
Benzoic Acid ◽  
Low Frequency ◽  
Temperature Dependent

Some Rationale for the Unusual Behavior of the Dielectric Constant of Cu2O

1973 ◽  
Vol 51 (6) ◽  
pp. 680-685 ◽  
Author(s):  
F. L. Weichman
Keyword(s):  
Dielectric Constant ◽  
High Frequency ◽  
Low Temperatures ◽  
Low Frequency ◽  
Depletion Layer ◽  
Temperature Dependent ◽  
Unusual Behavior ◽  
Temperature Variations ◽  
Very Low Frequency ◽  
Semiconducting Material

The very low frequency dielectric constant in Cu2O varies over wide limits and is highly temperature dependent. At sufficiently low temperatures the dielectric constant for all samples reduces to the high frequency value of about 7.5. Small variations in the high frequency value are easily explained as being due to the known presence of copper crystals embedded in the semiconducting material. The low frequency and temperature variations will be related to the variation in the depletion layer formed around each copper inclusion. Calculations are based on highly oversimplified size, shape, and distribution of the copper inclusions.

Temperature-dependent EXAFS study of the local structure and lattice dynamics in cubic Y2O3

2016 ◽  
Vol 23 (2) ◽  
pp. 510-518 ◽  
Author(s):  
Inga Jonane ◽  
Karlis Lazdins ◽  
Janis Timoshenko ◽  
Alexei Kuzmin ◽  
Juris Purans ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Temperature Dependence ◽  
Local Structure ◽  
Lattice Dynamics ◽  
Reverse Monte Carlo ◽  
Temperature Dependent ◽  
X Ray ◽  
Exafs Study ◽  
X Ray Absorption ◽  
Reverse Monte Carlo Method

The local structure and lattice dynamics in cubic Y2O3were studied at the YK-edge by X-ray absorption spectroscopy in the temperature range from 300 to 1273 K. The temperature dependence of the extended X-ray absorption fine structure was successfully interpreted using classical molecular dynamics and a novel reverse Monte Carlo method, coupled with the evolutionary algorithm. The obtained results allowed the temperature dependence of the yttria atomic structure to be followed up to ∼6 Å and to validate two force-field models.

Two temperature regimes of triplet transfer in the dissociation of the correlated triplet pair after singlet fission

2019 ◽  
Vol 97 (6) ◽  
pp. 465-473 ◽  
Author(s):  
Tia S. Lee ◽  
YunHui L. Lin ◽  
Hwon Kim ◽  
Barry P. Rand ◽  
Gregory D. Scholes
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Temperature Regime ◽  
Transient Absorption Spectroscopy ◽  
Type Model ◽  
Singlet Fission ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Pair Separation ◽  
Triplet Pair

The ability to undergo spin-allowed exciton multiplication makes singlet fission materials promising for photovoltaic applications. Here, we examine the separation of correlated triplet pairs, 1(T…T), in polycrystalline pentacene films via temperature-dependent transient absorption spectroscopy. Single wavelength analysis reveals a profound delay in 1(T…T) dynamics. Moreover, the dynamics of 1(T…T) exhibit temperature dependence, whereas other features show no discernable temperature dependence. Previous literatures have suggested that correlated triplet separation is mediated by a thermally activated hopping process. Surprisingly, we found that the time constants governing triplet pair separation display two distinct temperature-dependent regimes of triplet transport. The high temperature regime follows a thermally activated hopping mechanism. The experimentally derived reorganization energy and electronic coupling is verified by density matrix renormalization group quantum chemical calculations. In addition, we evaluated the low temperature regime and show that the trend can be modelled by a Miller–Abrahams-type model that incorporates the effects of energetic disorder. We conclude that the correlated triplet pair separation is mediated by thermally activated hopping or a disorder driven Miller–Abrahams-type mechanism at high and low temperature, respectively. We observe that crossover between two regimes occurs ∼226 K. We find the time constant for triplet–triplet energy transfer to be 1.8 ps at ambient temperature and 21 ps at 77 K.

Low Frequency Mechanical Spectroscopy of High Damping Mg-3wt.%Ni Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 1761-1764
Author(s):  
Di Qing Wan ◽  
Ya Juan Liu
Keyword(s):  
Grain Boundary ◽  
Low Frequency ◽  
Mechanical Analysis ◽  
Mechanical Spectroscopy ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Ni Alloy ◽  
Dislocation Movement ◽  
Boundary Relaxation ◽  
Two Peaks

The Dynamic Mechanical Analysis (DMA) was applied to investigate the low frequency mechanical spectroscopy response of as-cast high damping Mg-3wt.%Ni hypoeutectic alloys. There are two peaks appearing on the temperature dependent damping spectrum (-100 - 420 °C). The broad peak P1 is overlapped by some small peaks due to the thermally activated dislocation movement, while the P2 peak is a solute grain boundary relaxation peak.

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