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This paper presents a comprehensive analysis, carried out by the molecular dynamics (MD) simulations, of the vibrations of silicon nanowire (SiNW) resonators, having diverse applications including biological and medical fields. The chosen approach allows us to obtain a better understanding of the nanowire (NW) materials' characteristics, providing a more detailed insight into the behavior of nanostructures, especially when the topic of interest is relevant to their dynamics, interatomic interactions, and atoms trajectories' prediction. We first simulate a SiNW to study its frequency of vibrations using MD simulations. Then, we add a molecule of human immunodeficiency virus as an example to investigate the potential of the SiNW resonator for the detection of tiny bio-objects. The developed technique and its application to the detection of tiny objects, such as viruses, are discussed in the context of several key effects pertinent to the design of SiNW. [ABSTRACT FROM AUTHOR]

γ-Mg2SiO4 is an important mineral in mantle, and our knowledge on its mechanical and thermal properties is critical for many areas of geological sciences. In this work, the crystal structure of γ-Mg2SiO4 under high temperature and high pressure conditions is optimized by using the GOMASC method, and the total energy, thermal expansion coefficients, and elastic constants at different temperature and pressure conditions are obtained. On the basis of phonon spectrum, group velocity, phase velocity, Grüneisen parameter, and thermal conductivity are calculated for γ-Mg2SiO4 under high temperature and high pressure conditions. These calculated results can provide an important reference for geological research. [ABSTRACT FROM AUTHOR]

In the current paper, the ageing and de-ageing phenomena in ferroelectric ceramics are modelled by a Landau-type model based on the internal bias field theory. A new phenomenological term for the internal bias electrical field is added into the free energy function to simulate the phenomenon of lattice symmetry during the ageing phenomenon. The simulations for both ageing and de-ageing phenomena are successfully presented in the current paper. The hysteretic behaviours of the ageing and de-ageing phenomena are captured very well by the proposed model. [ABSTRACT FROM AUTHOR]

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ~1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode. [ABSTRACT FROM AUTHOR]

The new contribution of this paper is to develop a cylindrical representation of an already known multiphysics model for embedded nanowire superlattices (NWSLs) of wurtzite structure that includes a coupled, strain dependent 8-band k·p Hamiltonian in cylindrical coordinates and investigate the influence of coupled piezo-electromechanical effects on the barrier localization and critical radius in such NWSLs. The coupled piezo-electromechanical model for semiconductor materials takes into account the strain, piezoelectric effects, and spontaneous polarization. Based on the developed 3D model, the band structures of electrons (holes) obtained from results of modeling in Cartesian coordinates are in good agreement with those values obtained from our earlier developed 2D model in cylindrical coordinates. Several parameters such as lattice mismatch, piezo-electric fields, valence, and conduction band offsets at the heterojunction of AlxGa1-xN/GaN superlattice can be varied as a function of the Al mole fraction. When the band offsets at the heterojunction of AlxGa1-xN/GaN are very small and the influence of the piezo-electromechanical effects can be minimized, then the barrier material can no longer be treated as an infinite potential well. In this situation, it is possible to visualize the penetration of the Bloch wave function into the barrier material that provides an estimation of critical radii of NWSLs. In this case, the NWSLs can act as inversion layers. Finally, we investigate the influence of symmetry of the square and cylindrical NWSLs on the band structures of electrons in the conduction band. [ABSTRACT FROM AUTHOR]

Based on the first principles calculation combined with quasi-harmonic approximation in this work, we focus on the analysis of temperature dependent lattice geometries, thermal expansion coefficients, elastic constants, and ultimate strength of graphene and graphyne. For the linear thermal expansion coefficient, both graphene and graphyne show a negative region in the low temperature regime. This coefficient increases up to be positive at high temperatures. Graphene has superior mechanical properties with Young's modulus E = 350.01 N/m and ultimate tensile strength of 119.2 GPa at room temperature. Based on our analysis, it is found that graphene's mechanical properties have strong resistance against temperature increase up to 1000 K. Graphyne also shows good mechanical properties with Young's modulus E = 250.9 N/m and ultimate tensile strength of 81.2 GPa at room temperature, but graphyne's mechanical properties have a weaker resistance with respect to the increase of temperature than that of graphene. [ABSTRACT FROM AUTHOR]

Shape memory alloy (SMA) is a very important smart material, which has been widely used in many fields, especially in vibration. Phase transformation can be induced by changing temperature and its stiffness changes accordingly. In this paper, the primary resonance vibration of a one-dimensional SMA oscillator is analyzed using the harmonic balance (HB) method. The amplitude-frequency curves of the SMA oscillator with different temperatures are drawn, and the effect of temperature and frequency on the amplitude is discussed. Then, the energy flow of SMA in the vibration process is researched by the power flow analysis (PFA) approach. The time-averaged input power (TAIP) is calculated using the analytical and numerical method, respectively, and the calculation time is compared. It is found that the difference between the analytical and numerical solutions is not significant in most cases, but the calculation time of analytical solution is only about one-tenth of that of the numerical solution, which is very important in saving computational cost, real-time control and so on. Finally, some other characteristics of energy flow in the SMA oscillator are identified. [ABSTRACT FROM AUTHOR]