Graphic Characterization and Clustering Configuration Descriptors of Determinant Space for Molecules.

Quantum Monte Carlo approaches based on stochastic sampling of determinant space have evolved to be powerful methods to compute the electronic states of molecules. These methods not only calculate the correlation energy at an unprecedented accuracy but also provide insightful information on the electronic structures of computed states, for example, the population, connection, and clustering of determinants, which have not been fully explored. In this work, we devise a configuration graph for visualizing determinant space, revealing the nature of the molecule's electronic structure.

Towards an accurate description of one-dimensional pnictogen allotropes in nano-confinements.

One-dimensional (1D) confined pnictogen shows a diverse range of allotropes and potential applications in electronic devices and the chemical industry. Here, we report a theoretical study aimed at an accurate assessment of the thermodynamic stability of pnictogen structures under nano-meter confinements. We develop a cylindrical potential for pnictogen, which can be integrated with density functional theory to model a confined system towards achieving accuracy.

General Analytical Nuclear Forces and Molecular Potential Energy Surface from Full Configuration Interaction Quantum Monte Carlo.

The full configuration interaction quantum Monte Carlo (FCIQMC) is a state-of-the-art stochastic electronic structure method, providing a methodology to compute FCI-level state energies of molecular systems within a quantum chemical basis. However, especially to probe at the FCIQMC level, it is necessary to devise more efficient schemes to produce nuclear forces and potential energy surfaces (PES) from FCIQMC. In this work, we derive the general formula for nuclear forces from FCIQMC, and clarify different contributions of the total force.

A full configuration interaction quantum Monte Carlo study of ScO, TiO, and VO molecules.

Accurate ab initio calculations of 3d transition metal monoxide molecules have attracted extensive attention because of their relevance in physical and chemical science as well as theoretical challenges in treating strong electron correlation. Meanwhile, recent years have witnessed the rapid development of the full configuration interaction quantum Monte Carlo (FCIQMC) method to tackle electron correlation. In this study, we carry out FCIQMC simulations to ScO, TiO, and VO molecules and obtain accurate descriptions of 13 low-lying electronic states (ScO Σ, Δ, Π; TiO Δ, Δ, Σ, Π, Φ; VO Σ, Φ, Π, Γ, Δ), including states that have significant multi-configurational character.