Assessment, improvement, and comparison of different computational tools used for the simulation of heat transport in nanostructures

In this work we compare different implementations of two interatomic potential models, one the empirical Tersoff–Brenner and the other the semi-empirical tight-binding, to be used in the thermal transport study of silicon nanosystems. The calculations are based on molecular dynamics simulations. In the case of Tersoff–Brenner potential, two free software packages were used, while for tight-binding potential, an in-house code was developed. Both approaches require an enormous amount of computing effort, so the use of acceleration tools for adequate performance is crucial. We present a detailed study of each computational tool used: efficiency, advantages and disadvantages, and the results of application to the calculation of thermal conductance of structured silicon nanocrystals subjected to a temperature gradient.

Energy stability and electronic properties of carbon nanotorus at a localized breaking of interatomic bonds: computer modeling

This paper is devoted to the study of the dynamic processes that occur in the carbon nanotorus during localized breaking of interatomic bonds, and to the analysis of the influence of these processes on the electronic properties of carbon nanotorus. The object of research is a carbon nanotorus with chirality indices (13, 0) with a diameter of 20 nm and a thickness of 1 nm obtained as a result of defect-free folding of a zigzag carbon nanotube of appropriate geometric dimensions into a ring. The behavior of the nanotorus is modeled by the molecular dynamics method using a modified Brenner potential to describe the interaction between atoms. It is shown that over time, the nanotorus straightens into a nanotube, while maintaining energy stability. It is found that the process of nanotorus straightening is accompanied by the appearance of deformation wave-like bends propagating at a speed of 200 m/s along the atomic network of the structure. These bends lead to deformation of the nanotorus and numerous local breaks in the bonds between atoms. However, broken bonds are restored within a few femtoseconds before the structure relaxes in energy, therefore, in general, the atomic framework of the nanotorus remains defect-free after rectification. The results of calculating the distribution of the density of electronic states (DOS) of a nanotorus by the self-consistent charge density functional tight-binding (SCC-DFTB) quantum method showed that at the moment of localized breaking of interatomic bonds around the circumference of the tubular framework, the nanotorus loses its semiconductor properties, becoming a gapless conductor. The discovered physical phenomenon explains the process of nanotorus formation during synthesis accompanied by multiple ruptures of the nanotori and reverse closure of the nanotubes into the nanotori.

Investigation of Effect of Pore Shape, Position and Passivation on the Thermoelectric Properties of Porous Armchair Silicene Nanoribbons

In this paper, thermoelectric properties of porous armchair silicene nanoribbons (ASiNRs) have been investigated as a function of pore shape, position and passivation using the Non-equilibrium Green’s function (NEGF) method and Extended Huckel Technique (EHT). Here, nanopores of circular, rectangular, rhombus and triangular nature at different positions have been incorporated with an intention to optimize the structure for maximum thermoelectric figure of merit. In addition, the effect of passivation of the pore edges on the thermoelectric performance has been studied for all the shapes. Further, the effect of temperature variation on the thermoelectric efficiency has been studied. Ballistic transport regime and semi-empirical method using Huckel basis set are used to obtain the electrical properties, while the Brenner potential is used for the phononic system.

ADSORPTION OF C60 FULLERENE ON DEFECT-FREE GRAPHENE

Different ways of C60 fullerene adsorption on surface of defect-free graphene have been studied by the methods of computer simulation within the framework of the Brenner potential. The energies of binding and distance of adsorption have been obtained. It has been also studied how geometry of adsorbed fullerene depends on a way of adsorption.

The effect of imposed temperature difference on thermal conductivity in armchair single-walled carbon nanotube

Thermal conductivity of carbon nanotubes depends on various factors. The simulation of heat transport in armchair single-walled carbon nanotube by direct nonequilibrium molecular dynamics (NEMD) method employing Tersoff–Brenner potential indicates that, thermal conductivity decreases with increase in temperature difference between two ends of the tube. Increasing the imposed temperature differential along the tube axis, leads to domination of Umklapp scattering and impacts the heat transport. The applied temperature difference does not influence the behavior of thermal conductivity vs. tube length, diameter and temperature, but changes its value.