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The Massively Parallel Quantum Chemistry (MPQC) program is a 30-year-old project that enables facile development of electronic structure methods for molecules for efficient deployment to massively parallel computing architectures. Here, we describe the historical evolution of MPQC's design into its latest (fourth) version, the capabilities and modular architecture of today's MPQC, and how MPQC facilitates rapid composition of new methods as well as its state-of-the-art performance on a variety of commodity and high-end distributed-memory computer platforms. [ABSTRACT FROM AUTHOR]

Mesh-free particle methods applied to continuum fluid dynamics still use fictitious, ghost or virtual particles, and/or molecular dynamics concepts in the treatment of the boundaries. The aim of this paper is to present the implementation of the physical reflective boundary conditions (RBC), based on Newton's restitution law and the foundations of analytical geometry, in the treatment of contours in a three-dimensional (3D) domain. In a previous paper [C. A. D. Fraga Filho, "An algorithmic implementation of physical reflective boundary conditions in particle methods: Collision detection and response," Phys. Fluids 29, 113602 (2017)], RBC validation tests and simulation results were presented for a two-dimensional (2D) domain. The current work presents the validation of the collision detection and response algorithm employed for the RBC and its application in two cases (hydrostatics and hydrodynamics) in a 3D domain. Following an analysis of the simulation results, the applicability of the RBC to 3D continuum fluid dynamic problems is verified. In the hydrostatics case, a still liquid (Newtonian, incompressible, uniform, and isothermal) inside an immobile reservoir is studied. The fluid flow is modeled using an improved Smoothed Particle Hydrodynamics (SPH) formulation utilizing a modified concept of pressure. The simulation results are excellent, showing complete agreement with the analytical solution and the nonmotion of the particles throughout the simulation time. In the hydrodynamics case, 3D dam break flow modeling is carried out using the standard SPH formulation. Results provided by the RBC and standard SPH modeling are compared with the literature data demonstrating good agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

In this paper, an amorphous Ga2O3 metal–semiconductor–metal photodetectors passivated by the organosilicon layer were reported. Due to the excellent passivation property of the passivation layer and the diffusion effect of hydrogen, the responsivity of Ga2O3 photodetectors was improved effectively, while the dark state current is basically unchanged. The results of x-ray photoelectron spectroscopy have proved that the amount of oxygen vacancy near the interface between organosilicon and Ga2O3 layer has been passivated and the surface chemisorption was suppressed via capping a foreign layer after the deposition of organosilicon passivation layer. The Ga2O3 photodetectors with organosilicon passivation layer exhibit a boosted performance, with a low dark current of 2.96 × 10−12 A, a responsivity of 11.82 A/W, and a specific detectivity of 9.01 × 1014 Jones. [ABSTRACT FROM AUTHOR]

Multicomponent alloying has displayed extraordinary potential for producing exceptional structural and functional materials. However, the synthesis of single-phase, multi-principal covalent compounds remains a challenge. Here, we present a diffusion-controlled alloying strategy for the realization of covalent multi-principal transition metal carbides (MPTMCs) with a single face-centered cubic phase. The increased interfacial diffusion promoted by the addition of a nonstoichiometric compound leads to rapid formation of the single phase at much lower sintering temperature. Direct atomic-level observations via scanning transmission electron microscopy demonstrate that MPTMCs are composed of a single phase with a random distribution of all cations, which holds the key to the unique combinations of improved fracture toughness, superior Vickers hardness, and extremely lower thermal diffusivity achieved in MPTMCs. The present discovery provides a promising approach toward the design and synthesis of next-generation high-performance materials. [ABSTRACT FROM AUTHOR]

We present an energy-dependent explicitly correlated (F12) formalism for the nondiagonal renormalized second-order (NR2) Green's function method of closed-shell molecules. For a test set of 21 small molecules, the mean basis set error in IP computed using NR2-F12 with aug-cc-pVTZ basis is 0.028 eV, compared to 0.044 eV for NR2 with aug-cc-pV5Z basis. Similarly, for a set of 24 medium-sized organic electron acceptor molecules (OAM24), the mean basis set errors are 0.015 eV for NR2-F12 with aug-cc-pVTZ basis compared to 0.067 eV for NR2 with aug-cc-pVQZ basis. Hence, NR2-F12 facilitates accurate calculation of IP at a lower cost compared to the NR2 method. NR2-F12 has O ( N 6 ) / O ( N 5 ) noniterative/iterative costs with system size. At a small basis, the performance of NR2-F12 for 21 small molecules and OAM24 dataset is comparable to equation-of-motion ionized coupled-cluster singles and doubles, whose cost is iterative O ( N 6 ). [ABSTRACT FROM AUTHOR]