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Thermal conductivity of the Si nanowires with carbon concentration in three crystallography directions. The Tersoff potential is employed to define interactions
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In this paper, we investigate the thermal transport in Si nanowires by using nonequilibrium molecular dynamics simulations (NEMD). We focus on the effects of axial torsion and impurity on the thermal conductivity of the Si nanowires. Stillinger–Weber interatomic potential is employed to describe the interaction between silicon atoms. Also, Tersoff...
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... the disorder concentration varies from 0% to 6%. The thermal conductivity of the disordered Si nanowire is computed by employing theTersoff potential. The results are illustrated in Fig. 4 for three crystallography directions [100], [110] and [111]. We see that the thermal conductivity of pure Si nanowires, obtained by the Tersoff potential, is in the interval of 5-7.5 W/mK, namely, one to two orders of magnitude smaller than the corresponding results for bulk Si ...
Context 2
... results represents that trends of the three curves can be rather similar, but the [110] direction has a conductivity that is larger than the other crystallography directions, that is roughly 1.5 times more than [100] direction. As it is illustrated in Fig.4, by introducing the impurity to the Si nanowire, for instance at [110] direction, we can control the thermal conductivity in the range of 2.5-7.5 Wm -1 K -1 . ...
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Citations
... The Debye temperature for graphene is equal to 1813 K [54]. Khalkhali and Khoeini [55] investigated the quantum temperature and phonon spectrum of Si nanowires by MD simulation. In the presented research, the temperature difference in the Si nanowires is considered. ...
An oscillator is a circuit that can produce a continuous, repetitive, and alternating waveform without any input. However, the oscillations caused by the conversion between the two forms of energy cannot last forever. As a result , the amplitude decreases until it becomes zero, thus causing their nature to decrease. After discovering graphene nanosheets, their use in nanoelectricity science was much considered. Due to the amazing properties of graphene nanosheets, they can be used to establish permanent oscillations. The results show that graphene nanosheets ' mechanical properties and electrical properties depend on their structure and shape. Therefore, this study investigates the effect of graphene nanosheets type, size, and temperature on the simulated nanostructure's mechanical properties and oscillating behavior with Molecular Dynamics simulation. The results show that the graphene nanosheets with zigzag edges has higher mechanical strength than armchair edges. Young's modulus and Ultimate strength of graphene nanosheets with zigzag edges are numerically 1079 and 115 GPa, respectively. On the other hand, the resistance in graphene nanosheets can be expressed by reducing the oscillation amplitude and increasing the oscillation frequency. The results show that by changing the armchair edges to zigzag, the oscillation amplitude of graphene nanosheets decreases from 10.36 to 9.82 Å. Also, by enhancing the length of graphene nanosheets from 30 to 100, the oscillation amplitude of graphene nanosheets increases from 7.59 to 12.12 Å. This increase is due to the increases in the contact surface of the atomic structures. Consequently, the interactions between the carbon particles and mechanical resistance decrease. According to the results of this project , the findings improve the dynamics of nanoscale oscillators and cause a significant improvement in the performance of various devices.
... It is important to note that at temperatures below the Debye temperature, quantum corrections for MD calculations of temperature and thermal conductivity may be necessary [27]. Using Materials Studio CASTEP, we calculated the Debye temperature of our unit cell at approximately 1800 K, which is close to the Debye temperature of graphene 2000 K. Following the method described in [27], we checked for quantum corrections that might have been required. ...
... It is important to note that at temperatures below the Debye temperature, quantum corrections for MD calculations of temperature and thermal conductivity may be necessary [27]. Using Materials Studio CASTEP, we calculated the Debye temperature of our unit cell at approximately 1800 K, which is close to the Debye temperature of graphene 2000 K. Following the method described in [27], we checked for quantum corrections that might have been required. The temperature range in our simulations is below 500 K and as shown in figure 3, no quantum corrections are needed for classical MD temperatures below 600 K. ...
Manipulating the thermal conductivity of nanomaterials is an efficacious approach to fabricate tailor-made nanodevices for thermoelectric applications. To this end, superlattice nanostructures can be used to achieve minimal thermal conductivity for the employed nanomaterials. Two-dimensional biphenylene is a recently-synthesized sp2-hybridized allotrope of carbon atoms that can be employed in superlattice nanonstructures and therefore further investigation in this context is due. In this study, we first determined the thermal conductivity of biphenylene at 142.8 W.m-1.K-1 which is significantly lower than that of graphene. As a second step, we studied the effect of the superlattice period ( ) on thermal conductivities of the employed graphene/biphenylene superlattice nanoribbons, using the molecular dynamics simulation. We calculated a minimum thermal conductivity of 105.5 W.m-1k-1 at = 5 nm which indicates an achieved thermal conductivity reduction of approximately 97% and 26% when compared to pristine graphene and biphenylene, respectively. This superlattice period denotes the phonon coherent length at which the wave-like behavior of phonons starts prevailing over the particlelike behavior. Finally, the effects of temperature and temperature gradient on the thermal conductivity of superlattice were also investigated.
... The large reduction of j is attributed to the amorphous atomic arrangements, which encumber the formation of delocalized phonons and lead to intrinsically short phonon MFP. In the RNEMD framework, no quantum correction at low temperatures is considered, 37 since it is assumed to be negligible for amorphous materials; 17,38 further studies are needed to fully resolve the low-temperature thermal conductivities. The higher j of MAC compared with that of ma-BN may be due to the longer carrier MFP [see Fig. S1(a)]. ...
Amorphous materials feature localization of electrons and phonons that alter the electronic, mechanical, thermal, and magnetic properties. Here, we report calculations of the in-plane thermal conductivities of monolayer amorphous carbon and monolayer amorphous boron nitride, by reverse nonequilibrium molecular dynamics simulations. We find that the thermal conductivities of both monolayer amorphous carbon (MAC) and monolayer amorphous boron nitride (ma-BN) are about two orders of magnitude smaller than their crystalline counterparts. Moreover, the ultralow thermal conductivities are independent of the temperature and strain due to their extremely short heat carrier mean free paths. The relation between the structure disorder and the reduction of the thermal conductivity is analyzed in terms of the vibrational density of states and the participation ratio. The ma-BN shows strong vibrational localization across the frequency range, while the MAC exhibits a unique extended G * diffuson mode due to its sp ² hybridization and the broken E 2 g symmetry. The irregular vibrational patterns are also analyzed. The present results may enable potential applications of MAC and ma-BN in thermal management.
... The results showed that the EPI had a significant impact on the room temperature thermal conductivity of the material [23]. M. Khalkhali, et al. studied the relationship between molecular dynamics temperature and quantum temperature and obtained more accurate simulations of heat transport in silicon nanowires through quantum correction, which had an important significance for the molecular dynamics calculations below Debye temperature [24]. ...
... Where the v(t) and v(0) are velocities of the atom at the moments t and 0, respectively; and 〈…〉 denotes the averaged time and number of atoms. PDOS, which provides the total concentration of available states in a specific range of frequency, is calculated by taking the Fourier transform of VACF as (Khalkhali and Khoeini, 2018): ...
In the present work, the thermal properties of crystalline α-quartz, including thermal conductivity (TC) and thermal expansion coefficient (TEC), are studied using the non-equilibrium molecular dynamics (NEMD) simulation method. Since there is a dependence on interatomic potentials in simulation results, the thermal conductivity and thermal expansion coefficient of crystalline α-quartz is computed using various force fields in a temperature range from 200 K to 1000 K compared to which concurs better with experimental findings. Arising from the present molecular dynamic simulation by different force fields such as Tersoff, Vashishta, Stillinger-Weber, Meam, BKS, ReaxFF, and Morse, the thermal conductivities that were carried out using the ReaxFF and BKS are more accurate. It is also founded that predicted thermal conductivity at higher temperatures shows a better agreement with experimental values. In term s of TEC, Tersoff and SW corroborate the experimental remarks and give a smaller magnitude of TEC in the z-direction. On the other hand, in contradiction with the other force fields, Meam potential presents no significant TEC variation with temperature alteration.
... Nanowires (NWs) have currently attracted a great deal of interest in industry and academia because of their wide range of applications such as transparent electrodes, wearable electronics, solar cells, and light-emitting diodes [1][2][3][4][5][6][7] due to their characteristics such as high surface to volume ratio, low mass, high crystallinity, and directional electron transport [8][9][10]. Au-Ag heterogeneous NWs, as a typical representative of nanostructured materials, have become promising candidates in exploiting excellent multifunctional electronics and in fabricating new generation Micro/Nano devices due to their unique properties arising from the effective coupling of different domains [10][11][12][13][14][15]. ...
... The beginning of the plastic deformation arises from the emergence of the first 1/6 <112> Shockley incomplete dislocation ( Fig. 4(a)), which nucleates in the Au segment. The dislocation then slips on <111> plane in the Au segment with the beginning of the plastic deformation of the NW [12]. When the strain reaches point b, the 1/6 <112> Shockley incomplete dislocation penetrates the Au segment and leaves the extrinsic stacking fault (Fig. 4(b)). ...
... Similarly, the 1/6 <112> Shockley incomplete dislocation (Fig. 4(d)) nucleates from the free surface. Later, the dislocation glides on the plane towards to the other side of the surface, generating the extrinsic stacking fault (Fig. 4(e)) [12]. Finally, through the interaction of multiple dislocations, an intrinsic stacking fault emerges and passes through the whole NW, inducing the necking of the surface. ...
The tensile process of nanowires (NWs), in which one end of a NW is fixed, and the load is applied to the other end, is investigated via molecular dynamics (MD). Here, we pay attention to length-dependent mechanical properties of heterostructured Au-Ag NWs under the above tensile form. It was discovered that all the samples became stronger except for the shortest one with the length of 4 nm and the load on the Ag end with the decrease of length. Meanwhile, we found that all samples with the load on Ag ends outperformed the same NWs with the load on Au ends in terms of yield strengths and elongations. Meanwhile, the NWs with the load on Ag ends may exhibit a better performance in terms of conductivity. A reasonable analysis from the perspective of radial distribution function has been developed to explain above phenomena.
... The effects of strain on the thermal behavior of the two-and threedimensional nanostructures were reported in the literature [37][38][39][40][41][42][43][44][45]. It is worth noting that with increasing the tensile strain in the nanostructure, the thermal conductivity generally decreases. ...
... The same behavior was reported for graphene nanoribbons, as well [37]. However, sometimes increasing positive strain caused to increase and then decrease the thermal conductivity [38,40,44] and this behavior was justified by the crystallography directions, strain range, functional groups, etc. In our study, as shown in Fig. 6, the effective thermal conductivity and consequently, the thermal conductivity increase with increasing the tensile strain. ...
... Therefore, because of the broad potential application of silicene-based nano-devices, studying the thermal transport behavior of silicene nanotubes and engineering its thermal conduction properties to use for a diverse range of applications may be an exciting challenge. Among various factors, the effect of strain, isotope doping, grain boundary, defects and impurity, crystal structures, temperature, torsion, and size on the thermal conductivity of nanostructures have attracted great deals of attention during the last decade [41][42][43]. ...
... Therefore, the reduction in the thermal conductivity of A-Z GSNTs compared with ASNTs and ZSNTs can be attributed to the existence of the grain boundary and consequently boundary thermal resistance. To examine the sensibility of the thermal conductivity to the mean temperature of the silicene nanotubes, we enhance the mean temperature from 300 to 700 K. Two possibility occurs with increasing the mean temperature of a system; i.e., increasing the phonon-phonon scattering and increasing the excited high-energy (high frequency) phonons [41]. Fig. 7 presents that the thermal conductivity of the silicene nanotubes decreases by increasing the temperature. ...
Thermal transport behavior in silicene nanotubes has become more important due to the application of these promising nanostructures in the engineering of next-generation nanoelectronic devices. We apply non-equilibrium molecular dynamics (NEMD) simulations to study the thermal conductivity of silicene nanotubes with different lengths and diameters. We further explore the effects of grain boundary, strain, vacancy defect, and temperature in the range of 300–700 K on the thermal conductivity. Our results indicate that the thermal conductivity varies with the length approximately in the range of 24–34 W/m K but exhibits insensitivity to the diameter and chirality. Besides, silicene nanotubes consisting of the grain boundary exhibit nearly 30% lower thermal conductivity compared with pristine ones. We discuss the underlying mechanism for the conductivity suppression of the system consisting of the grain boundary by calculating the phonon power spectral density. We find that by increasing the defect concentration and temperature, the thermal conductivity of the system decreases desirably. Moreover, for strained nanotubes, we observe unexpected changes in the thermal conductivity, so that the conductivity first increases significantly with tensile strain and then starts to decrease. The maximum thermal conductivity for the armchair and zigzag edge tubes appears at the strains about 3% and 5%, respectively, which is about 28% more than that of the unstrained structure.
... This behavior is in a better agreement with previous studies for different systems. 71,72 Here, we studied the influence of distance between two consecutive 5-8-5 defects (parameter S is shown in Fig. 1) on thermal conductivity for samples with the length 40nm. Larger parameter S causes the concentration of 5-8-5 defects reduces. ...
Understanding the influence of defects on thermal conductivity of nanowires and nanomaterials is important due to its application for heat management in the nanodevices. In the present study, we investigate the influence of topological line defects on thermal conductivity of single-walled carbon nanotube (SWCNT) through molecular dynamics simulations. To model interaction between carbon atoms in the carbon nanotube, we employed the three-body Tersoff potential. Thermal conductivity was obtained in situations, which the 5-8-5 defects have been distributed with several patterns on the surface of carbon nanotube (CNT). We examined the impact of defect concentration and found that thermal conductivity decreases with increasing defect concentration. We also investigated the effects of length, temperature and the temperature difference between two ends of carbon nanotube on its thermal conductivity. The increase of length leads to an increment in thermal conductivity, while the increase of temperature causes thermal conductivity decreases. The cross-section of the nanotubes changes with the pattern of defect. Our results can be applicable in the heat management of carbon nanotube-based nanodevices.
... The In order to achieve a better elucidate of governed physical phenomena, we have calculated phonon density of states of two groups of atoms, belonging to two sides of the grain boundary. The phonon power spectral density has been obtained by computing the Fourier transform of autocorrelation function of the velocity of atoms corresponding to two sides of the grain boundary as follow [60,61]: ...
During the fabrication process of large scale silicene through common chemical vapor deposition (CVD) technique, polycrystalline films are quite likely to be produced, and the existence of Kapitza thermal resistance along grain boundaries could result in substantial changes of their thermal properties. In the present study, the thermal transport along polycrystalline silicene was evaluated by performing a multiscale method. Non-equilibrium molecular dynamics simulations (NEMD) was carried out to assess the interfacial thermal resistance of various constructed grain boundaries in silicene as well as to examine the effects of tensile strain and the mean temperature on the interfacial thermal resistance. In the following stage, the effective thermal conductivity of polycrystalline silicene was investigated considering the effects of grain size and tensile strain. Our results indicate that the average values of Kapitza conductance at grain boundaries at room temperature were estimated nearly 2.56*10^9 W/m2K and 2.46*10^9 W/m2K through utilizing Tersoff and Stillinger-Weber interatomic potentials, respectively. Also, in spite of the mean temperature whose increment does not change Kapitza resistance, the interfacial thermal resistance can be controlled by applying strain. Furthermore, it was found that, by tuning the grain size of polycrystalline silicene, its thermal conductivity can be modulated up to one order of magnitude.
