Heat capacity and low-frequency vibrational density of states. Inferences for the boson peak of silica and alkali silicate glasses

2009 ◽  
Vol 404 (20) ◽  
pp. 3799-3806 ◽  
Author(s):  
Nicolas F. Richet
Keyword(s):  
Heat Capacity ◽  
Density Of States ◽  
Low Frequency ◽  
Boson Peak ◽  
Silicate Glasses ◽  
Vibrational Density Of States ◽  
Alkali Silicate ◽  
Vibrational Density

scholarly journals Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity – the Boson peak of PIM-1

2018 ◽  
Vol 20 (3) ◽  
pp. 1355-1363 ◽  
Author(s):  
Reiner Zorn ◽  
Huajie Yin ◽  
Wiebke Lohstroh ◽  
Wayne Harrison ◽  
Peter M. Budd ◽  
...  
Keyword(s):  
Density Of States ◽  
Low Frequency ◽  
Boson Peak ◽  
Vibrational Density Of States ◽  
First Time ◽  
Intrinsic Microporosity ◽  
Vibrational Density

For the first time the low frequency vibrational density of states is reported for a polymer with intrinsic microporosity.

scholarly journals Heat capacity anomalies of the molecular crystal 1-fluoro-adamantane at low temperatures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daria Szewczyk ◽  
Jonathan F. Gebbia ◽  
Andrzej Jeżowski ◽  
Alexander I. Krivchikov ◽  
Tatiana Guidi ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Low Temperature ◽  
Density Of States ◽  
Molecular Crystal ◽  
Molecular Crystals ◽  
Disordered Materials ◽  
Vibrational Density Of States ◽  
Disorder Phase Transition ◽  
Optical Modes ◽  
Vibrational Density

AbstractDisorder–disorder phase transitions are rare in nature. Here, we present a comprehensive low-temperature experimental and theoretical study of the heat capacity and vibrational density of states of 1-fluoro-adamantane (C10H15F), an intriguing molecular crystal that presents a continuous disorder–disorder phase transition at T = 180 K and a low-temperature tetragonal phase that exhibits fractional fluorine occupancy. It is shown that fluorine occupancy disorder in the low-T phase of 1-fluoro-adamantane gives rise to the appearance of low-temperature glassy features in the corresponding specific heat (i.e., “boson peak” -BP-) and vibrational density of states. We identify the inflation of low-energy optical modes as the main responsible for the appearance of such glassy heat-capacity features and propose a straightforward correlation between the first localized optical mode and maximum BP temperature for disordered molecular crystals (either occupational or orientational). Thus, the present study provides new physical insights into the possible origins of the BP appearing in disordered materials and expands the set of molecular crystals in which “glassy-like” heat-capacity features have been observed.

Low frequency vibrational density of state of highly permeable super glassy polynorbornenes – the Boson peak

2020 ◽  
Vol 22 (33) ◽  
pp. 18381-18387
Author(s):  
Reiner Zorn ◽  
Paulina Szymoniak ◽  
Mohamed A. Kolmangadi ◽  
Marcell Wolf ◽  
Dmitry A. Alentiev ◽  
...  
Keyword(s):  
Density Of States ◽  
Time Of Flight ◽  
Low Frequency ◽  
Boson Peak ◽  
Density Of State ◽  
Neutron Time ◽  
Incoherent Neutron ◽  
Vibrational Density

Inelastic incoherent neutron time-of-flight scattering was employed to measure the low frequency density of states for a series of addition polynorbornenes with bulky side groups.

A Low Frequency Study of the Vibrational Modes in Alkalisilicate Glasses by Raman Spectroscopy

1995 ◽  
Vol 407 ◽  
Author(s):  
R. Sommer ◽  
J. Toulouse ◽  
H. Jain
Keyword(s):  
Raman Spectroscopy ◽  
Force Constant ◽  
Density Of States ◽  
System Analysis ◽  
Low Frequency ◽  
Boson Peak ◽  
Single Parameter ◽  
Silicate Glasses ◽  
Vibrational Modes ◽  
Peak Region

ABSTRACTWe have performed a study on low frequency modes in several alkali silicate glasses by Raman spectroscopy. The Boson peak region is analyzed with a single parameter ω0 which is believed to characerize the density of states of the system. Analysis of the dependence of ω0 on the nature and concentration of the alkali suggests that the position of the Boson peak is essentially governed by the ratio “force constant” over “mass” of localized oscillator modes. At lower frequency (below 30 cm−1), the “excess” intensity can be explained by considering secondorder processes of the same vibrational modes, superimposed on other (possibly relaxational) modes.

scholarly journals Universal law for the vibrational density of states of liquids

2021 ◽  
Vol 118 (5) ◽  
pp. e2022303118
Author(s):  
Alessio Zaccone ◽  
Matteo Baggioli
Keyword(s):  
Density Of States ◽  
Normal Modes ◽  
Low Frequency ◽  
Average Lifetime ◽  
Vibrational Density Of States ◽  
Lennard Jones ◽  
Average Relaxation Time ◽  
Universal Law ◽  
Infinite Set ◽  
Vibrational Density

An analytical derivation of the vibrational density of states (DOS) of liquids, and, in particular, of its characteristic linear in frequency low-energy regime, has always been elusive because of the presence of an infinite set of purely imaginary modes—the instantaneous normal modes (INMs). By combining an analytic continuation of the Plemelj identity to the complex plane with the overdamped dynamics of the INMs, we derive a closed-form analytic expression for the low-frequency DOS of liquids. The obtained result explains, from first principles, the widely observed linear in frequency term of the DOS in liquids, whose slope appears to increase with the average lifetime of the INMs. The analytic results are robustly confirmed by fitting simulations data for Lennard-Jones liquids, and they also recover the Arrhenius law for the average relaxation time of the INMs, as expected.

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