The wetting behavior of spherical nanoparticles at a vapor-liquid interface is investigated by using density functional theory, and the line tension calculation method is modified by analyzing the total energy of the vapor-liquid-particle equilibrium. Compared with the direct measurement data from simulation, the results reveal that the thermodynamically consistent Young's equation for planar interfaces is still applicable for high curvature surfaces in predicting a wide range of contact angles. The effect of the line tension on the contact angle is further explored, showing that the contact angles given by the original and modified Young's equations are nearly the same within the region of 60° < θ < 120°. Whereas the effect is considerable when the contact angle deviates from the region. The wetting property of nanoparticles in terms of the fluid-particle interaction strength, particle size, and temperature is also discussed. It is found that, for a certain particle, a moderate fluid-particle interaction strength would keep the particle stable at the interface in a wide temperature range.

A large bulk band gap and tunable Dirac carriers are desired for practical device applications of topological insulators. However, most known topological insulators are narrow gap materials and the manipulation of their Dirac surface states is limited by residual bulk charge carriers originating from intrinsic defects. In this study, via density functional theory based first-principles calculations, we predict that a layered hexagonal structure of BiS is stable, and it becomes a topological insulator under a moderate compressive pressure of about 5.3 GPa. Interestingly, we find that the strength of the spin-orbit interaction in BiS can be effectively enhanced by the applied pressure. This leads to an increased inverted band gap with pressure, which can reach 0.4 eV with a pressure of 13.7 GPa. Compared to BiSe, intrinsic defects are suppressed in BiS under both cation- and anion-poor growth conditions. Our calculations predict a new Bi-based topological insulator, and also shed light on control over spin-orbit interactions in BiS and tuning of its topological properties.

An improved direct correlation function is proposed and applied to construct an accurate free energy functional. The theoretical method is extended to analyze the pore size distributions (PSDs) of both slit-and cylindricalshaped carbonaceous materials. With the same parameters for the fluid and material as in the simulation, the model is much more advantageous than the known density functional methods for calculating the adsorption isotherms in individual pores. The overall PSDs for two model carbons are evaluated for CH 4 , CF 4 , and SF 6 absorbates, and good results are obtained. The results are reliable because the two model carbons have structures that are exactly known. Encouraged by the success with slit pores, we further extend the model to the internal cylindrical space of a single-walled carbon nanohorn. The PSDs of the carbon nanohorn are evaluated, and satisfactory results are again obtained.

In this work, a weighted density functional theory has been used to study the equilibrium and metastable processes for argon. In the theoretical approach, the two- and three-body interactions of the fluid molecules are considered simultaneously, and the renormalization group transformation is applied to address the long-range fluctuations inside the critical region. The global phase equilibria, planar and curvature-dependent surface tensions, critical radius, and nucleation rates of argon are investigated systematically. The results are in good agreement with the experimental data. Meanwhile, this work applies a methodology for calculating the curved surface tension in local supersaturated environments, showing that the Tolman length is negligible far from the critical region. Near the critical point, however, the Tolman length becomes positive and appears to diverge.