Density of Phonon States in Cubic Ice Ic

The measurement of the H-projected density of phonon states (H-DOPS) of polycrystalline ice Ic has been performed with an unprecedented accuracy, and in a sample having an almost perfect crystallographic purity, as it was obtained from the transformation of ice XVII. Results are compared with new accurate measurements of H-DOPS in ice Ih, and with centroid molecular-dynamics (MD) computations. The differences between the experimental H-DOPS in these two forms of ice are subtle, but quantitatively measurable. In addition, they are reproduced semi-quantitatively by computational methods, demonstrating the effectiveness of this innovative simulation tool for reproducing the dynamical properties of the ice structures.

Density of Phonon States in Cubic Ice Ic

The measurement of the H-projected density of phonon states (H-DOPS) of polycrystalline ice Ic has been performed with an unprecedented accuracy, and in a sample having an almost perfect crystallographic purity, as it was obtained from the transformation of ice XVII. Results are compared with new accurate measurements of H-DOPS in ice Ih, and with centroid molecular-dynamics (MD) computations. The differences between the experimental H-DOPS in these two forms of ice are subtle, but quantitatively measurable. In addition, they are reproduced semi-quantitatively by computational methods, demonstrating the effectiveness of this innovative simulation tool for reproducing the dynamical properties of the ice structures.

Особенности перколяционной схемы перестройки колебательного спектра сплава с составом для Ga-=SUB=-1-x-=/SUB=-Al-=SUB=-x-=/SUB=-P

Specific features of the properties of Ga–P lattice vibrations have been investigated using the percolation model of a mixed Ga_1 – x Al_ x P crystal (alloy) with zero lattice mismatch between binary components of the alloy. In contrast to other two-mode alloy systems, in Ga_1 – x Al_ x P a percolation splitting of δ ~ 13 cm^–1 is observed for the low-frequency mode of GaP-like vibrations. An additional GaP mode (one of the percolation doublet components) split from the fundamental mode is observed for the GaP-rich alloy, which coincides in frequency with the gap corresponding to the zero density of one-phonon states of the GaP crystal. The vibrational spectrum of impurity Al in the GaP crystal has been calculated using the theory of crystal lattice dynamics. Upon substitution of lighter Al for the Ga atom, the calculated spectrum includes, along with the local mode, a singularity near the gap with the zero density of phonon states of the GaP crystal, which coincides with the mode observed experimentally at a frequency of 378 cm^–1 in the Ga_1 – x Al_ x P ( x < 0.4) alloy.

Numerical Study on Thermal Boundary Resistance and Conductive Properties of Cu/Al Interface

In this paper, the thermal boundary resistance and conductive properties of Cu/Al interface are investigated by using first-principles calculations based on density functional theory (DFT) with considering the pressure influence. Based on the atomic model of Cu/Al interface the simulation results show that the lattice parameters for both Cu and Al are sensitive to pressure and density states of Cu/Al interface increase as pressure increases from 0 to 5 GPa. Although Cu and Al have the same atomic structure, the significant differences of the density of phonon states lead to the thermal resistance that exists at the Cu/Al interface. At the Cu/Al interface, Cu and Al atoms can diffuse into each other and form an alloy-like interfacial region. The change of the copper component in the alloy can considerably affect the conductive properties of Cu/Al interface.

SURFACE PHONONS IN THE ORDERED c(2 × 2) PHASE OF Pd ON Au(100)

The vibrational properties of the Au(100)-c(2 × 2)-Pd ordered phase, which is a stable system in the temperature range of 500 K to 600 K, are presented. This surface alloy is formed by depositing Pd atoms onto the Au(100) surface, and annealing at higher temperatures. The equilibrium structural characteristics, phonon dispersions as well as the local density of phonon states are calculated using the matching theory associated with Green's function formalism evaluated in the harmonic approximation. New surface modes have been found on the ordered metallic surface alloy along the three directions of high symmetry [Formula: see text], [Formula: see text], and [Formula: see text], in comparison with the clean surface Au(100) . Three of them are observed above the bulk bands spectrum.

THE VIBRATIONAL DYNAMICS OF THE ORDERED METALLIC Pd/Cu(100) SURFACE ALLOYS

The vibrational properties of the three ordered metallic surface alloys, Cu(100) -c(2 × 2)- Pd , Cu(100)-(2 × 1)-Pd , and Cu(100)-(2 × 2)-Pd , are presented. The phonon dispersions of vibrational modes as well as the local density of phonon states (LDOS) are calculated using matching theory associated with Green's function formalism. The calculated results are discussed and interpreted. In particular, the transfer of charge between the Pd and Cu atoms in the surface alloys modifies the surface boundary force constants, with resultant remarkable differences for the vibrational LDOS on the Pd and Cu atomic sites at the Pd/Cu(100) surface, compared to the LDOS at the pure Cu(100) surface. This may favor new Pd -catalyzed reactions at such surface alloys systems.