We present a calculation for the vibrational properties of the ordered surface alloy Au(110)-1×2-Pd on a crystalline substrate of Au. The surface phonon dispersion curves and the local vibrations densities of states (LDOS) are calculated in the harmonic approximation for the system, using the phase field matching theory (PFMT) method and associated real space Green’s functions. In particular, it is shown that the surface alloy presents optic vibrational modes above the Au bulk bands, along the directions of high-symmetry [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] of the corresponding two-dimensional Brillouin zone. Measurements of the surface phonon dispersion branches can hence be made by different techniques such as helium atom scattering (HAS) to compare with. The calculated LDOS for Au and Pd atomic sites in the four top surface atomic layers span a wider range of frequencies than those for the individual Au(110) or Pd(110) metallic surfaces. These LDOS provide a spectral signature for the progressive transition from the surface dynamics to that of the Au crystal bulk. Knowledge of these LDOS for the surface alloy can also serve as an input for modeling the diffusion and reaction rates of chemical species at its surface.
A theoretical approach for the study of phonon dynamics and scattering properties of doped transpolyacetylene chain is presented. The coherent reflection and transmission scattering cross-sections for phonons incident on the doped unit cell boundary are calculated in accordance with the Landauer-Buttiker electron scattering description, using the matching procedure with the nearest and next nearest neighbor elastic force constants. This is done for two different dopants, namely, the potassium and sodium atoms. Our numerical results yield an understanding of the transpolyacetylene chain dynamical properties and the effects on phonon conductance due to phonon incident on the doped unit cell boundary. The coherent reflection and transmission coefficients show characteristic spectral features, depending on the cutoff frequencies for the propagating phonons and on the nature of the dopants. They illustrate the occurrence of Fano resonances in the scattering spectra that result from the interactions of propagating elastic waves of the undoped transpolyacetylene chain with the localized modes due to the breakdown of the translation symmetry in the x direction.
This work constitutes an analysis of the thermodynamic properties in the ordered metallic surface alloy system Au(111)-([Formula: see text])[Formula: see text]-Pd. The equilibrium structural characteristics as well as the thermodynamic functions are examined by the matching method, associated with real space Green’s function formalism, evaluated in the harmonic approximation. Our numerical results, for this metallic system of surface alloy, show in particular a significant dependence between the thermodynamic properties and the coordination number and the values of the force constants.
A theoretical model is presented for the study of magnons heat transfer across an integrated nanostructure acting as interface material between two ultrathin Heisenberg ferromagnetic films. This is done by calculating the transmission rates of the spin wave modes through the consideration of the magnon group velocity modification in the system. The group velocities are calculated explicitly for all propagating frequencies and spin wave incidence angles. The matching method is used with nearest neighbor ferromagnetic interactions to calculate the coherent transmission coefficients for magnons incident on the nanostructure boundaries. They are investigated for different nanostructure thickness over the entire propagating frequency range of the system, in order to calculate the heat transport across the nanostructure. The model is applied to a system of three Iron ferromagnetic atomic layers and Gadolinium integrated nanostructure. The thermal conductivities are numerically calculated for individual magnon modes of the system. The results yield an understanding of the relationship between the magnons thermal conductivity of the system and the structural configuration of the integrated nanostructure.
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