Understanding the nature of chemical bonding in solids is crucial to comprehend the physical and chemical properties of a given compound. To explore changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O), a combination of property-, bond breaking- and quantum-mechanical bonding descriptors have been applied. The outcome of our explorations reveals an electron transfer driven transition from metavalent bonding in PbX (X = Te, Se, S) to iono-covalent bonding in beta-PbO. Metavalent bonding is characterized by adjacent atoms being held together by sharing about a single electron and small electron transfer (ET). The transition from metavalent to iono-covalent bonding manifests itself in clear changes in these quantum-mechanical descriptors (ES and ET), as well as in property-based descriptors (i.e. Born effective charge, dielectric function, effective coordination number (ECON) and mode-specific Grueneisen parameter, and in bond breaking descriptors (PME). Metavalent bonding collapses, if significant charge localization occurs at the ion cores (ET) and/or in the interatomic region (ES). Predominantly changing the degree of electron transfer opens possibilities to tailor materials properties such as the chemical bond and electronic polarizability, optical band gap and optical interband transitions characterized by the imaginary part of the dielectric function. Hence, the insights gained from this study highlight the technological relevance of the concept of metavalent bonding and its potential for materials design.
Electronic Structure, mass fluctuation, and Localized Bond Properties of two-dimensional double-layer transition metal chalcogenide MX$_2$ (M = Mo, W; X = S, Se, Te) Calculated Based on Density Functional Theory and BBC model
Chemical Migration and Dipole Formation at van der Waals Interfaces between Magnetic Transition Metal Chalcogenides and Topological Insulators
金属和磁性覆盖层通过邻近效应而且通过改变Bi $_2$ Se $_3$子表面的组成和化学结构来改变拓扑绝缘体（TI）硒化铋（Bi $_2$ Se $_3$）的表面。采用X射线光电子能谱学（XPS）研究了Bi $_2$ Se $_3$和Mn金属或硒化锰之间的界面，揭示了界面处的化学和电子变化。在没有外部Se源的情况下，在Bi $_2$ Se $_3$上沉积Mn金属显示出由于Mn-Se键合而在Mn层内的意外键合，因为Se从Bi $_2$ Se $_3$层扩散到生长的Mn膜中。Se向外扩散进一步通过Bi $_2$ Se $_3$层内Bi核心能级的变化来证明，这表明主要是Bi-Bi键合超过Bi-Se键合。当过量的Se与Mn一起供应时，没有发生Se的外扩散，这表明为沉积的金属提供足够的硫族元素原子的重要性。然而，Bi $_2$ Se $_3$核心水平光电子表现出刚性化学位移朝向更高的结合能后，沉积单层的MnSe $_{2-x}$，表明在覆盖层内的偶极子。化学计量计算表明，单层形成MnSe优先于过渡金属二硫属化物（TMD）相MnSe $_2$，提供了一致的图片的偶极子形成中，一个平面的Se阴离子位于Mn阳离子。这项研究表明，化学扩散和偶极子的形成是很重要的Mn-Bi $_2$ Se $_3$和MnSe $_{2-x}$ -Bi $_2$ Se $_3$和TMD/TI接口更普遍应仔细考虑。
An experimental and computational investigation of structure and magnetism in pyrite Co$_{1-x}$Fe$_x$S$_2$: Chemical bonding and half-metallicity
制备了黄铁矿硫属化合物固溶体Co $_{1-x}$ Fe $_x$ S $_2$ 0 <= x <= 0.5的块状样品，用X射线衍射和SQUID磁化强度测量研究了它们的晶体结构和磁性。在整个溶液系列中，过硫化物（S $_2^{2-}$）单元中硫原子之间的距离几乎保持恒定。使用实验晶体结构作为输入的第一原理电子结构计算指出了这种恒定的S-S距离的重要性，有助于反键S-S能级钉扎费米能量。相反，假设的岩盐CoS不是一个好的半金属，尽管几乎是等结构和等电子的。我们利用我们对Co $_{1-x}$ Fe $_x$ S $_2$系统的理解，为新的铁磁半金属制定了一些规定。
Observation of Iso-Symmetric Structural and Lifshitz Transitions in Quasi-one-dimensional CrNbSe$_5$
Michigan State University（密歇根州立大学）；Ames National Laboratory（艾姆斯国家实验室）；Iowa State University（爱荷华州立大学）；University of South Carolina（南卡罗来纳大学）；Harvard University（哈佛大学）
X-ray photo-induced atomic motion in Phase Change Materials and conventional covalent chalcogenide glasses
Institut Néel, Université Grenoble Alpes and Centre National de la Recherche Scientifique（尼斯研究所，格勒诺布尔阿尔卑斯大学及法国国家科学研究中心）；Department of Physics, University of Trento（特伦托大学物理系）；Department of Chemistry, Aarhus University（奥胡斯大学化学系）；European Synchrotron Radiation Facility（欧洲同步辐射装置）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；ICGM, Université de Montpellier, CNRS, ENSCM（材料化学与全球分子实验室，蒙彼利埃大学，法国国家科学研究中心及国立化学学院）
