Surface-states of topological insulators are assumed to be robust against non-magnetic defects in the crystal. However, recent theoretical models and experiments indicate that even non-magnetic defects can perturb these states. Our first-principles calculations demonstrate that the presence of Se vacancies in Bi$_2$Se$_3$, has a greater impact than a mere n-doping of the structure, which would just shift the Fermi level relative to the Dirac point. We observe the emergence of a non-linear band pinned near the Fermi level, while the Dirac cone shifts deeper into the valence band. We attribute these features in the bandstructure to the interaction between the surface and defect states, with the resulting hybridization between these states itself depending on the position and symmetry of the Se vacancy relative to the surfaces. Our results bring us a step closer to understanding the exotic physics emerging from defects in Bi$_2$Se$_3$ that remained unexplored in prior studies.
The surface functionalization of diamond has been extensively studied through a variety of techniques, such as oxidation. Several oxygen groups have been correspondingly detected on the oxidized diamond, such as COC (ester), CO (ketonic), and COH (hydroxyl). However, the composition and relative concentration of these groups on diamond surfaces can be affected by the type of oxygenation treatment and the diamond surface quality. To investigate the stability of the oxygenated groups at specific diamond surfaces, we evaluated through fully atomistic reactive molecular mechanics (FARMM) simulatio…
The development of efficient photoelectrodes via defect engineering of wide-band gap metal oxides has been the prime focus for many years. Specifically, the effect of carbon defects in wide-band gap metal oxides on their performance in photoelectrochemical (PEC) applications raised numerous controversies and still elusive. Herein, the effect of various carbon defects in m-ZrO2 was investigated using the density functional theory to probe the thermodynamic, electronic, and optical properties of the defective structures against pristine m-ZrO2. The defect formation energies revealed that elevati…
Fundamental understanding of the reactivity between coating material of Li-ion battery cathode and electrolyte is important in order to obtain suitable coating candidates. Herein, we study ethylene carbonate (EC) adsorption and decomposition reactions on pristine, O vacancy- and Zn vacancy-defected ZnO (10-10) by means of first-principles density functional theory (DFT) calculations. Possible decomposition pathways via H-abstraction and EC ring-opening reaction that leads to the generation of CO2 and C2H4 gases are studied from the thermodynamic and kinetic aspects. Firstly, we find that molec…
Electronic Properties of Defective MoS$_{2}$ Monolayers Subject to Mechanical Deformations: A First-Principles Approach
第六族过渡金属二硫属化合物（transition metal dichalcogenides，TMD）单层膜是一种具有直接带隙的二维半导体材料，在纳米电子学、光电子学等领域具有广阔的应用前景。这些单分子层可以经历强的弹性形变，高达约10\%，而没有任何键断裂。此外，电子结构和输运性质，这定义了纳米电子器件中的这些TMD单层的性能，可以强烈地受到点缺陷的存在下，这是经常存在于合成样品。因此，重要的是要了解这两种影响的电子性质的单分子膜。在这项工作中，我们研究了缺陷的MoS $_{2}$单分子膜的电子结构和能量特性，受到各种应变，使用密度泛函理论模拟。我们的研究结果表明，应变导致带隙内的缺陷能级及其轨道特性的强烈修改。应变还分裂的退化缺陷能级高达450 meV的量，提出了新的应用。
A machine-learned spin-lattice interatomic potential (MSLP) for magnetic iron is developed and applied to mesoscopic scale defects. It is achieved by augmenting a spin-lattice Hamiltonian with a neural network term trained to descriptors representing a mix of local atomic configuration and magnetic environments. It reproduces the cohesive energy of BCC and FCC phases with various magnetic states. It predicts the formation energy and complex magnetic structure of point defects in quantitative agreement with density functional theory (DFT) including the reversal and quenching of magnetic moments…
