Prof. Mohan Chen and his collaborators recently adopted computational simulation methods to predict the atomic-scale disordered hyperuniform (DHU) state of materials. The work was published by Science Advances on April, 17th, 2020.

DHU is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems, and has been applied to a wide range of scientific research areas such as materials sciences and biological systems, etc. DHU systems are characterized by vanishing infinite-wavelength normalized density fluctuations and are endowed with unique novel physical properties. The team reported the discovery of DHU in atomic-scale two-dimensional materials, i.e., amorphous silica composed of a single layer of atoms.

The research team built an atomic model through high-resolution transmission electron microscope images, and adopted classical molecular dynamics and density functional theory to predict the DHU state of two-dimensional SiO₂ and compute its electronic structure. Moreover, it’s shown that DHU leads to almost complete closure of the electronic bandgap compared to the crystalline counterpart, making the material effectively a metal. This is in contrast to the conventional wisdom that disorder generally diminishes electronic transport and is due to the unique electron wave localization induced by the topological defects in the DHU state.

Fig. A: Power spectra of two-dimensional SiO₂ that has a disordered hyperuniform state. B: Electron density around the Fermi level of two-dimensional SiO₂ that has a disordered hyperuniform state. The blue and red atoms depict Si and O atoms, respectively.

Traditional density functional theory (DFT) packages typically adopt plane wave basis set, leading to a high computational cost for large systems. In this work, the researchers used a DFT package named ABACUS (Atomic-orbital Based Ab-initio Computation at USTC), which was developed by Prof. Chen and his collaborators from scratch. ABACUS utilizes systematically improvable optimized numerical atomic orbitals as basis set, and is capable of simulating large-size systems with relatively lower computational costs than the traditional DFT packages. This work involves full quantum mechanics simulations of a two-dimensional disordered SiO₂ system that consists of 1,800 atoms, their work demonstrates that ABACUS is more efficient than traditional DFT packages. They conclude that ABACUS is a competitive DFT package as compared with other DFT packages.

Prof. Mohan Chen from Center of Applied Physics and Technology, Peking University, Prof. Houlong Zhuang from Arizona State University, Prof. Yang Jiao from Arizona State University, and Prof. Wenxiang Xu from Hohai University are co-corresponding authors of this work, other collaborators are from University of Science and Technology of China, University of Pennsylvania, and Carnegie Mellon University.

Link of the manuscript: https://advances.sciencemag.org/content/6/16/eaba0826#aff-2