Amorphous red phosphorus (a-P) is one of the remaining puzzling cases in the structural chemistry of the elements. Here, we elucidate the structure, stability, and chemical bond-ing in a-P from first principles, combining machine-learning and density-functional theo-ry (DFT) methods. We show that a-P structures exist with a range of energies slightly higher than those of phosphorus nanorods, to which they are closely related, and that the stability of a-P is linked to the degree of structural relaxation and medium-range order. We thus complete the stability range of phosphorus allotropes [Angew. Chem. Int. Ed. 2014, 53, 11629] by now including the previously poorly understood amorphous phase, and we quantify the covalent and van der Waals interactions in all main phases of phos-phorus. We also study the electronic densities of states, including those of hydrogenated a-P. Beyond the present study, our structural models are expected to enable wider-ranging first-principles investigations - for example, of a-P-based battery materials.
Amorphous phosphorus (a-P) has long attracted interest because of its complex atomic structure, and more recently as an anode material for batteries. However, accurately describing and understanding a-P at the atomistic level remains a challenge. Here we show that large-scale molecular-dynamics simulations, enabled by a machine learning (ML)-based interatomic potential for phosphorus, can give new insights into the atomic structure of a-P and how this structure changes under pressure. The structural model so obtained contains abundant five-membered rings, as well as more complex seven- and eig…
Two pressure-induced phase transitions have been theoretically studied in the layered iron phosphorus triselenide (FePSe3). Topological analysis of chemical bonding in FePSe3 has been performed based on the results of first-principles calculations within the periodic linear combination of atomic orbitals (LCAO) method with hybrid Hartree-Fock-DFT B3LYP functional. The first transition at about 6 GPa is accompanied by the symmetry change from R-3 to C2/m, whereas the semiconductor-to-metal transition (SMT) occurs at about 13 GPa leading to the symmetry change from C2/m to P-31m. We found that t…
On the basis of density functional calculations and using Bader's atom in molecule theory, this article presents quantitative microscopic analyses on the bonding properties of amorphous silicon (a-Si) which could reflect in the observable mechanical and electronic behaviors of this material. In addition, the occurrence and strength of quantum confinement of charge carriers in a composition of silicon crystal nano slabs (SiNSs) embedded in hydrogenated a-Si (a-Si:H) semiconductor are studied. It is shown that the strongest confinement effect happens for Si slabs limited in [100] direction. The …
The precise nature of chemical-bonding interactions in amorphous, and crystalline, chalcogenides is still unclear due to the complexity arising from the delocalization of bonding, and non-bonding, electrons. Although an increasing degree of electron delocalization for elements down a column of the periodic table is widely recognized, its influence on chemical-bonding interactions, and on consequent material properties, of chalcogenides has not previously been comprehensively understood from an atomistic point of view. Here, we provide a chemical-bonding framework for understanding the behaviou…
Lithium phosphorus oxynitride (LiPON) is an amorphous solid-state lithium ion conductor displaying exemplary cyclability against lithium metal anodes. There is no definitive explanation for this stability due to the limited understanding of the structure of LiPON. We provide a structural model of RF-sputtered LiPON via experimental and computational spectroscopic methods. Information about the short-range structure results from 1D and 2D solid-state nuclear magnetic resonance experiments investigating chemical shift anisotropy and dipolar interactions. These results are compared with first pri…
Competing covalent and ionic bonding in Ge-Sb-Te phase change materials
Ge 2Sb 2 Te 5和相关的相变材料是非常不寻常的，因为它们可以使用非常快的熔化、淬火、退火循环在非晶态和晶态之间容易地转变，尽管所产生的状态在环境温度下寿命极长。这些状态具有显著不同的物理性质，包括与常见的玻璃形成物（如硅酸盐或磷酸盐）形成强烈对比的可见光中非常不同的光学常数。这种行为已经被描述为共振键合，但仍然存在困惑，特别是关于结晶相和非晶相的不同物理性质。在这里，我们表明，在立方相的离子和共价键之间存在着强烈的竞争，提供了相变记忆性能的化学基础和压电材料（PbTiO 3，BiFeO 3）的巨大响应的起源之间的联系。这对动力学行为具有重要的影响，特别是导致相对于非晶，晶相中的声学模式的同时硬化和高频光学模式的软化。非晶相和结晶相中的这种不同键合提供了对不同物理性质的直接解释以及对长时间稳定性和快速切换的组合的理解，并且可用于发现具有优异性质的新相变组合物。
Amorphous solid water (ASW) is abundantly present in the interstellar medium, where it forms a mantle on interstellar dust particles and it is the precursor for cometary ices. In space, ASW acts as substrate for interstellar surface chemistry leading to complex molecules and it is postulated to play a critical role in proton-transfer reactions. Although ASW is widely studied and is generally well characterized by different techniques, energetically-induced structural changes, such as ion, electron and photon irradiation, in these materials are less well understood. Selective pumping of specifi…
Lamellar structures of transition metal phosphorus trisulfides possess strong intralayer bonding, albeit adjacent layers are held by weak van der Waals interactions. Those compounds received enormous interest due to their unique combination of optical and long-range magnetic properties. Among them, iron phosphorus trisulfide (FePS$_3$) gathered special attention for being a semiconductor with an absorption edge in the near-infrared, as well as showing an Ising-like anti-ferromagnetism. We report a successful growth of centimeter size bulk FePS$_3$ crystals with a chemical yield above 70%, whos…
Ultrananocrystalline diamond/hydrogenated amorphous carbon composite thin films synthesized via coaxial arc plasma possess a marked structural feature of diamond grains embedded in an amorphous carbon and a hydrogenated amorphous carbon matrix which are the largest constituents of the films. Since the amorphous nature yields much larger light absorption coefficients as well as a generation source of photo-induced carriers with UV rays, these films can be potential candidates for deep-UV photodetector applications. From some previous studies p-type conduction of the films has been realized by d…
Locally, the atomic structure in well annealed amorphous silicon appears similar to that of crystalline silicon. We address here the question whether a point defect, specifically a vacancy, in amorphous silicon also resembles that in the crystal. From density functional theory calculations of a large number of nearly defect free configurations, relaxed after an atom has been removed, we conclude that there is little similarity. The analysis is based on formation energy, relaxation energy, bond lengths, bond angles, Voronoï volume, coordination, atomic charge and electronic gap states. All thes…
College of Physics, Chengdu University of Technology（成都理工大学物理学院）；Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford（牛津大学化学系物理与理论化学实验室）；Laboratoire Charles Coulomb (L2C), University of Montpellier and CNRS（蒙彼利埃大学与法国国家科学研究中心夏尔·库隆实验室）
Electronic excitation of ultrafast collective amorphous-amorphous transitions in glassy phase-change material
Suzhou Institute for Advanced Research, University of Science and Technology of China（中国科学技术大学苏州高等研究院）；State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University（吉林大学电子科学与工程学院集成光电子学国家重点联合实验室）；Key Laboratory for Laser Plasmas (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院激光等离子体教育部重点实验室）；School of Integrated Circuits, Shanghai Jiao Tong University（上海交通大学集成电路学院）；Department of Physics, University of Science and Technology of China（中国科学技术大学物理系）；State Key Laboratory of Precision Spectroscopy, and School of Physics and Electronic Science, East China Normal University（华东师范大学物理与电子科学学院精密光谱科学与技术国家重点实验室）；Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University（上海交通大学张江高等研究院）
Predicting the Fracture Propensity of Amorphous Silica Using Molecular Dynamics Simulations and Machine Learning
Sibley School of Mechanical and Aerospace Engineering, Cornell University（康奈尔大学机械与航空航天工程学院）；Department of Engineering Mechanics, Xi’an Jiaotong University（西安交通大学工程力学系）
A quantitative understanding of the microscopic constraints which underlie a well relaxed glassy structure is the key to developing a microscopic theory of structural evolution and plasticity for the amorphous solid. Here we demonstrate the applicability of one such theory of local bonding constraints developed by D. R. Nelson [Phys. Rev. B 28, 5515 (1983)], for a model binary Lennard-Jones glass structure that has undergone an isothermal annealing simulation spanning over 10 micro-seconds of physical simulation time. By introducing a modified radical Voronoi tessellation which removes some am…
