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Anomalous thermal expansion behaviour of several open frame-work compounds has been extensively investigated using the techniques of inelastic neutron scattering and lattice dynamics. These compounds involve increasing level of structural…
Using the generalized Langevin equation formalism and the process of contraction of the description we derive a general memory function equation for the thermal fluctuations of the local density of a simple atomic liquid. From the analysis…
Inelastic neutron scattering is used to measure the temperature dependent phonon dispersion in Ca$_{2-x}$Sr$_{x}$RuO$_{4}$ ($x=0.4$, 0.6). The in-plane $\Sigma_{4}$ octahedral tilt mode softens significantly at the zone boundary of the high…
This paper derives a prediction for the variation of the amplitude of the dielectric loss from isomorph theory, and presents an experimental test of the prediction performed by measuring the dielectric-relaxation behavior of the van der…
Strong correlation between equilibrium fluctuations of the potential energy, U, and the virial, W, is a characteristic of a liquid that implies the presence of certain dynamic properties, such as density scaling of the relaxation times and…
In this letter, we systematically investigate the microscopic dynamics of collective vibrational excitations in simple liquids. The thermodynamic states of simple liquids are unified to the mean atomic free volume. Our results show that…
The elastic properties of hcp $^4$He samples have been investigated using low frequency (20 Hz to 20 kHz) high sensitivity sound transducers. In agreement with the findings of other workers, most samples studied grew very significantly…
The nonlinear dynamics of a one-dimensional molecular crystal in the form of a chain of planar coronene molecules is analyzed. Using molecular dynamics, it is shown that a chain of coronene molecules supports acoustic solitons,…
We observe magnetic effects in ultra-high quality factor crystalline quartz Bulk Acoustic Wave resonators at milli-Kelvin temperature. The study reveals existence of hysteresis loops, jumps and memory effects of acoustical resonance…
An analytical theory is presented for the damping of low-frequency adsorbate vibrations via resonant coupling to the substrate phonons. The system is treated classically, with the substrate modeled as a semi-infinite elastic continuum and…
A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations. Here, we report that the crystalline solid AgCrSe2 has liquid-like thermal conduction. In this compound, Ag…
The effective dynamic properties of specific periodic structures involving rubber-like materials can be adjusted by pre-strain, thus facilitating the design of custom acoustic filters. While nonlinear viscoelastic behaviour is one of the…
Heat conduction in dielectric crystals originates from the propagation of atomic vibrations, whose microscopic dynamics is well described by the linearized phonon Boltzmann transport equation. Recently, it was shown that thermal…
We have considered the relaxation of transverse thermal and high-frequency phonons for the Landau-Rumer mechanism in the semiconductor cubic crystals. Using the known values of these elastic moduli, the parameters determining the transverse…
Dielectric measurements on molecular liquids just above the glass transition indicate that alpha relaxation is characterized by a generic high-frequency loss varying as $\omega^{-1/2}$, whereas deviations from this come from one or more…
We present an extension of our recently introduced molecular density functional theory of water [G. Jeanmairet et al., J. Phys. Chem. Lett. 4, 619, 2013] to the solvation of hydrophobic solutes of various sizes, going from angstroms to…
We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultra-thin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe that the decay time…
The dynamic structure factor of the 7Li0.61Na0.39 liquid alloy at T=590 K has been calculated by ab initio molecular dynamics simulations using 2000 particles. For small wavevectors, 0.15 <= q/A-1 <= 1.6, we find clear side peaks in the…
Long wavelength acoustic phonons are normally weakly coupled to other vibrational modes in a crystalline system. This is particularly problematic in molecular dynamics calculations where vibrations at the system size scale are typically…
Comprehensive inelastic neutron-scattering measurements were performed to study the soft optical phonons in La2-xSrxCuO4 at x=0.10, 0.12 and 0.18. We found at x=0.18 that the softening of Z-point phonon, suggesting incipient structural…