A temperature behavior of the frustrated translational mode of adsorbate and the nature of the “adsorbate–substrate” interaction

Abstract

A temperature behavior of the frustrated translational mode of adsorbate and the nature of the "adsorbate-substrate" interaction V.V. IgnatyukInstitute for Condensed Matter Physics, 1 Svientsitskii Street, 79011, Lviv, Ukraine (Dated: August 6, 2017)A temperature behavior of the frustrated translational mode (T-mode) of a light particle, coupled by different regimes of ohmicity to the surface, is studied within a formalism of the generalized diffusion coefficients. The memory effects of the adsorbate motion are considered to be the main reason of the T-mode origin. Numerical calculations yield a thermally induced shift and broadening of the T-mode, which is found to be linear in temperature for Ohmic and super-Ohmic systems and nonlinear for strongly sub-Ohmic ones. We obtain analytical expressions for the T-mode shift and width at weak coupling for the systems with integer "ohmicity" indexes n = 0÷2 in zero temperature and high temperature limits. We provide an explanation of the experimentally observed blue-or red-shifts of the T-mode on the basis of a comparative analysis of two typical times of the system evolution: a time of decay of the "velocity-velocity" autocorrelation function, and a correlation time of the thermal bath random forces. A relation of the T-mode to the multiple jumps of the adsorbate is discussed, and generalization of conditions of the multiple hopping to the case of quantum surface diffusion is performed.

A simple ansatz for the study of velocity autocorrelation functions in fluids at different timescales

“…It is widely believed that the low frequency asymptote determines the long time behaviour of the corresponding TCF, and the cut-off frequency in the exponent of (3.11) can just slightly change the shape of TCF. However, in the theory of solids, it is reasonable [29,30] to consider the upper cut-off frequency ω c , associated, for instance, with the Debye frequency ω D , and to put J(ω) = 0 at ω > ω c , like it happens in the case under consideration. An advantage of our approach consists in the fact that the expression (3.10) has been obtained rigorously using the only assumption (3.1) for the SCFs of higher orders, and the cut-off frequency ω c has appeared in a natural way (not as a fitting parameter).…”

Jump diffusion in the strong-collision model on a two-dimensional triangular lattice

“…This interest lies in the variety of important physical applications that include Josephson Junctions, superionic conductors, adsorbates on crystal surfaces, and polymers diffusing at interfaces among many others [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. At low temperatures, k B T << E a (k B is the Boltzmann constant, T is the temperature, and E a is the height of the energy barrier) the diffusion proceeds by uncorrelated thermally activated jumps from one minimum of the potential to another, with a jump frequency that depends exponentially on E a according to the Arrhenius law.…”

Zubarev nonequilibrium statistical operator method in Renyi statistics. Reaction-diffusion processes

“…Reaction-diffusion and adsorption-desorption processes on the metal surface are nonlinear. They manifest an oscillation character, possess memory effects and are actual in terms of nanostructure formation on the surfaces occurring in catalytic phenomena [49][50][51][52][53][54][55][56].…”