Narrow Results

The classical molecular dynamics (MD) technique was used to investigate the atomistic structure of amorphous hafnium oxide (HfO₂) under pressure. The local atomic structure and the liquid-solid transition of HfO₂ were analyzed for the pair radical distribution functions, bond angle distributions and coordination number. The simulation reveals that although the fractions of structural units HfO${}_x$ and OHf${}_y$ strongly change with the density, the partial bond angle distributions of these structural units are almost identical for all constructed models. This result has enabled us to establish a relationship between the bond angle distributions and the fractions of structural units.

The gelation of waxy crude oil multiphase system can result in the formation of network cementitious structure, which seriously impacts the safe and economic production of crude oil. This paper reviews current experimental, theoretical and numerical results on the gelation of wax in crude oil. For the experimental side, the most important problems are in situ measurement and measurement accuracy. On the theoretical side, the present methods own defects of low accuracy and limited application scope. Numerically, the models are of oversimplification, which are hardly applied to the real production. Besides, as a promising solution, the research progress of crude oil pour point depressant is also reviewed. The molecular design is a powerful approach to develop the optimized pour point depressant. The goals of this paper are to bridge the microscale atomic interactions and the macroscale physicochemical properties of waxy crude oil and pour point depressant, so as to lay a solid theoretical basis for preventing and controlling wax deposition in crude oil. These are beneficial to the future efficient, clean and safe energy production system.

Titanium carbides were studied via molecular dynamics simulation to characterize TiC${}_x$ structures with respect to the carbon diffusion properties in this study. The effect of carbon concentration on atomic structures of titanium carbides was investigated through discussing the structure variation and the radial distribution functions of carbon atoms in titanium carbides. The carbon diffusion in titanium carbides was also analyzed, focusing on the dependence on carbon concentration and carbide structure. Carbon diffusivity with different carbon concentrations was determined by molecular dynamics (MD) calculations and compared with the available experimental data. The simulation results showed an atomic exchange mechanism for carbon diffusion in titanium carbide.

The evolution of atomic structures and its correlation with the kinetic fragility of liquid tantalum (Ta) during cooling were investigated through molecular dynamics simulations. Pair distribution function, angular distribution function, and largest standard cluster analysis were used to characterize the atomic configurations in the Ta metal system. Results revealed that canonical Kasper clusters with a coordination number of $\ge$12 play a critical role in the formation of Ta monoatomic metallic glasses. Similar to the pattern observed in many multi-component metallic glass-forming liquids, the three-stage evolution pattern of the self-diffusion coefficient could be observed during cooling. The fragile-to-strong (F–S) transition temperature of liquid Ta is identified to be $T_{\mathrm{\text{f-s}}}\approx 1.18T_g$. The possible structural reason for the strong-to-fragile liquid transition is correlated with the formation of abundant Kasper medium-range orders (MROs) and their zigzag competition with the loose configurations in liquid regions. The F–S transition is attributed to the success of MROs in the competition and their subsequent rapid growth.

Field-ion microscopy and molecular dynamics simulation were used for the characterization of the translation states at special grain boundaries in tungsten. It is revealed that rigid-body displacement had the component of displacement parallel to the [110] direction equal to 0 or 1 interplanar spacing. Full vectors of lateral shifts are described by broad statistical distribution. The mathematical simulation revealed two mirror-symmetry-breaking lateral translations along the direction of the Σ9 grain boundary corresponding to different atomic structures. It is shown that the partial disconnection with the Burgers vector can be considered as the elemental carriers of grain-boundary polymorphic transformation.

The nitride semiconducting materials are stable in the hexagonal wurtzite structure; they exhibit the largest extension of direct band gaps for one alloy family (AlN: 6.2 eV, GaN: 3.5, InN: 0.65), thus are able to cover from the UV to IR wavelength for emission and detection applications. They are obtained as thin layers mainly grown on foreign substrates. As these materials are expected to exhibit high thermal and mechanical stability in addition to the interesting electronic properties, they are due to find applications as high power high frequency components. However, the active parts are made of alloyed heterostructures, and the three compounds exhibit highly distinct physical properties. Therefore the assistance of structural investigations to the fabrication of the devices has been proven to be indispensable. In this work, we report part of our extensive investigations of the growth defects using transmission electron microscopy and theoretical modelling.

This chapter reveals how a core geosphere known as the Tau144/300 forms within the Context. Referred to as the Core, it is shown how a complex aggregation of points form edges and meet to give rise to three-dimensional interacting elements. Image intense, this chapter demonstrates how the Context and Core of the Matrix synchronise and sequentially harmonise discrete forms. The Core is also revealed to dynamically unify all forms, and generate a cluster of six Jitterbugs as compared to the five found in the Context. The relationship of the Core’s architecture, a dynamic, face-centred crystalline lattice, is explored with connections found in common with the atomic nucleus, quantum mechanics, diamonds, Earth’s planetary core and cell biology.

We present a mathematical view of the structure of matter based on the invariance of the classical equations of physics.

The classical molecular dynamics (MD) technique was used to investigate the atomistic structure of amorphous hafnium oxide (HfO₂) under pressure. The local atomic structure and the liquid-solid transition of HfO₂ were analyzed for the pair radical distribution functions, bond angle distributions and coordination number. The simulation reveals that although the fractions of structural units HfO_x and OHf_y strongly change with the density, the partial bond angle distributions of these structural units are almost identical for all constructed models. This result has enabled us to establish a relationship between the bond angle distributions and the fractions of structural units.