Quadratic scaling bosonic path integral molecular dynamics

Bosonic exchange symmetry leads to fascinating quantum phenomena, from exciton condensation in quantum materials to the superfluidity of liquid 4He. Unfortunately, path integral molecular dynamics (PIMD) simulations of bosons are computationally prohibitive beyond ∼100 particles, due to a cubic scaling with the system size. We present an algorithm that reduces the complexity from cubic to quadratic, allowing the first simulations of thousands of bosons using PIMD. Our method is orders of magnitude faster, with a speedup that scales linearly with the number of particles and the number of imaginary time slices (beads). Simulations that would have otherwise taken decades can now be done in days. In practice, the new algorithm eliminates most of the added computational cost of including bosonic exchange effects, making them almost as accessible as PIMD simulations of distinguishable particles.

Adsorption of toxic gases on borophene: surface deformation links to chemisorptions

β12 borophene has received great attention because of its intriguing mechanical and electronic properties. One of the possible applications of borophene is gas sensing. However, the interaction between common gases and β12 borophene remains to be clarified. In this work, we study the interactions of β12 borophene towards five hazardous gases, namely, CO, NO, NH3, NO2, and CO2 using various non-empirical van der Waals density functionals and provide an insight into the adsorption behavior of borophene. The adsorption mechanism and molecular vibrations are discussed in great detail. Among the gases considered, CO2 is physisorbed while other gases are chemically bonded to β12 borophene. We also demonstrate that the deformation at the ridge of borophene enables its active p z orbital to strongly hybridize with frontier orbitals of the studied polar gases. Consequently, borophene is predicted to interact strongly with CO, NO, NH3, and especially NO2, making it a sensitive sensing material for toxic gases.

Progress and challenges in ab initio simulations of quantum nuclei in weakly bonded systems

Atomistic simulations based on the first-principles of quantum mechanics are reaching unprecedented length scales. This progress is due to the growth in computational power allied with the development of new methodologies that allow the treatment of electrons and nuclei as quantum particles. In the realm of materials science, where the quest for desirable emergent properties relies increasingly on soft weakly bonded materials, such methods have become indispensable. In this Perspective, an overview of simulation methods that are applicable for large system sizes and that can capture the quantum nature of electrons and nuclei in the adiabatic approximation is given. In addition, the remaining challenges are discussed, especially regarding the inclusion of nuclear quantum effects (NQEs) beyond a harmonic or perturbative treatment, the impact of NQEs on electronic properties of weakly bonded systems, and how different first-principles potential energy surfaces can change the impact of NQEs on the atomic structure and dynamics of weakly bonded systems.