First principle study of the elastic properties of InGaAs with different doping concentrations of indium
The electronic structure and elastic properties of the InGaAs crystal with different doping concentrations of indium are studied by the plane-wave pseudopotential method based on density functional theory with Cambridge Serial Total Energy Package programme. The density of states and the elastic constants of the InGaAs crystal with different doping concentrations of indium are obtained. The elastic modulus is also calculated from the theoretical elastic constants by Voigt?Reuss?Hill averaging scheme. The band gaps of the InGaAs crystal decrease monotonically with increasing indium concentration. Similarly, the elastic constants of the InGaAs crystal with the symmetry of cubic crystal system decrease monotonically with increasing indium concentration. With increasing indium concentration, the brittleness of the InGaAs crystal decreases and the ductility of the InGaAs crystal increases monotonically, resulting in the tangential deformation of the supercells which is more prone to occur. The values of the elastic constants obtained will be helpful in analysing the elastic properties of InGaAs/GaAs semiconductor saturable absorber mirror and in guiding the application of InGaAs/GaAs as a saturable absorber in passively Q-switched laser.
CASTEP + DMol3
First-principle calculations of structural stabilities and elastic properties of Al2Sr and Mg2Sr phases
Structural stabilities, elastic properties and electronic structures of Mg17Al12, Al2Sr and Mg2Sr phases have been determined from first?principle calculations by using CASTEP and DMOL programs based on the density functional theory. The calculated formation heats and cohesive energies indicated that Al2Sr has the strongest alloying ability as well as the highest structural stability. The calculated Gibbs free energy showed that the structural stabilities of Mg17Al12, Al2Sr andMg2Sr change with elevated temperature, when the temperature is above 423 K, Al2Sr is more stable than Mg17Al12phase, and Sr addition to the Mg?Al base alloys can improve the creep properties. The calculated bulk modulus (B), anisotropy values (A), Young’s modulus (E), shear modulus (G) and Poisson ratio (ν) showed that Mg2Sr is ductile, on the contrary, Mg17Al12and Al2Sr are both brittle, and among the three phases Mg2Sr is a phase with the best plasticity. The calculations of the density of states (DOS) and Mulliken electronic populations showed that the reason of Al2Sr having the highest structural stability attributes to Al2Sr phase having the more covalent bonds compared with Mg17Al12 and Mg2Sr phases, while Mg17Al12 phase having more stable structure is the result of co?action of ionicand covalent bonds.
CASTEP + GULP
Computer simulation of Na-bearing majoritic garnet
On the difference in cycling behaviors of lithium-ion battery cell between the ethylene carbonate- and propylene carbonate-based electrolytes
Density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations have been performed to gain insight into the difference in cycling behaviors between the ethylene carbonate (EC)-based and the propylene carbonate (PC)-based electrolytes in lithium-ion battery cells. DFT calculations of the lithium solvation, Li+(S)i (S = EC or PC; i = 1?4) with and without the presence of the counter anion showed that the desolvation energy to remove one solvent molecule from the first solvation shell of the lithium ion was significantly reduced by as much as 70 kcal mol?1 (293.08 kJ mol?1) in the presence of the counter anion, suggesting the lithium ion is more likely to be desolvated at high salt concentrations. The thermodynamic stability of the ternary graphite intercalation compounds, Li+(S)iC72, in which Li+(S)i was inserted into a graphite cell, was also examined by DFT calculations. The results suggested that Li+(EC)iC72 was more stable than Li+(PC)iC72 for a given i. Furthermore, some of Li+(PC)iC72 were found to be energetically unfavorable, while all of Li+(EC)i=1?4C72 were stable, relative to their corresponding Li+(S)i in the bulk electrolyte. In addition, the interlayer distances of Li+(PC)iC72 were more than 0.1 nm longer than those of Li+(EC)iC72. MD simulations were also carried out to examine the solvation structures at a high salt concentration of LiPF6: 2.45 mol kg?1. The results showed that the solvation structure was significantly interrupted by the counter anions, having a smaller solvation number than that at a lower salt concentration (0.83 mol kg?1). We propose that at high salt concentrations, the lithium desolvation may be facilitated due to the increased contact ion pairs so as to form a stable ternary GIC with less solvent molecules without destruction of graphite particles, followed by solid?electrolyte-interface film formation reactions. The results from both DFT calculations and MD simulations are consistent with the recent experimental observations.
A density functional theory study on the Ti/P binary cluster ions
Under the framework of density functional theory, an all-electron calculation on the geometrical structures and dissociation channels of Ti/P binary cluster ions has been carried out. The P2, P3 and P4 structures are found to be the relatively stable units in these cluster ions. The lowest energy geometries of these Ti/P binary cluster ions may be constructed by bonding Ti, Ti2, Ti3 or Ti4 unit with one or two relatively stable P2, P3 and P4 units. The most possible dissociation channels of these Ti/P binary cluster ions are the detachment of P2, P3 or P4 fragment. It is well consistent with the photodissociation experimental results.
DMol3 + Forcite + Adsorption locator + QSAR
Quantitative Structure and Activity Relationship Modeling Study of Corrosion Inhibitors: Genetic Function Approximation and Molecular Dynamics Simulation Methods
QSAR studies on the inhibition corrosion efficiencies of twenty three organic compounds on steel surface in hydrochloric acid solutions using several physicochemical descriptors and investigation of the adsorption of these compounds on the steel surface by Monte Carlo simulation method were studied. Topological indices as well as several structural descriptors are used in the development of quantitative structure-activity relationships (QSARs) using genetic function approximation statistical analysis method. From our studies it is clear that quantum descriptors are a better choice when predictivity is the main issue. Among the descriptors with major contribution we should point out that lowest unoccupied molecular orbital energy (E(LUMO)) and molecular volume are important predictive descriptors. Computational studies have been used to find the most stable adsorption sites for tributlyamine inhibitor on steel surface.