Evolution of chemical bonding and electron density rearrangements during D3h → D3d reaction in monolayered TiS2: A QTAIM and ELF study

Monolayered titanium disulfide TiS₂, a prospective nanoelectronic material, was previously shown to be subject to an exothermic solid‐state D_3h–D_3d reaction that proceeds via a newly discovered transition state. Here, we study the reaction in detail using topological methods of quantum chemistry (quantum theory of atoms in molecules and electron localization function analysis) and show how electron density and chemical bonding between the atoms change in the course of the reaction. The reaction is shown to undergo a series of topological catastrophes, associated with elementary chemical events such as break and formation of bonds (including the unexpected formation of S? S bonding between sulfur layers), and rearrangement of electron density of outer valence and core shells. © 2014 Wiley Periodicals, Inc.     

C D : a computer program to generate 1D, 2D and 3D grids of functions dependent on the molecular ab initio electron density

A program to compute many functions dependent on the electron density ρ(r) from the results of ab initio molecular calculations is presented. The program allows the generation of different one-, two-, and three-dimensional grids for further graphical representation or numerical analysis. Other options like extracting separate atom contributions to the function computed or locating maximum and minimum values are also implemented. A number of illustrative applications regarding different ρ(r)-dependent functions are presented and the performance and portability of the program is discussed.     

Hybrid organic–inorganic CH3NH3PbI3 perovskite building blocks: Revealing ultra‐strong hydrogen bonding and mulliken inner complexes and their implications in materials design

Methylammonium lead iodide (CH₃NH₃PbI₃) perovskite compound has produced a remarkable breakthrough in the photovoltaic history of solar cell technology because of its outstanding device‐based performance as a light‐harvesting semiconductor. Whereas the experimental and theoretical studies of this system in the solid state have been numerously reported in the last 4 years, its fundamental cluster physics is yet to be exploited. To this end, this study has performed theoretical investigations using DFT‐M06‐2X/ADZP to examine the principal geometrical, electronic, topological, and orbital properties of the CH₃NH₃PbI₃ molecular building block. The intermolecular hydrogen bonded interactions examined for the most important conformers of the system are found to be unusually strong, with binding energies lying between −93.53 and −125.11 kcal mol⁻¹ (beyond the covalent limit, −40 kcal mol⁻¹), enabling us to classify the underlying interactions as ultra‐strong type since their characteristic properties are unidentical with those have already been proposed as very strong, strong, moderate, weak, and van der Waals. Based on this, together with the unusually high charge transfers, strong hyperconjugative interactions, sophisticated topologies of the charge density, and short intermolecular distances of separation, we have characterized the conformers of CH₃NH₃PbI₃ as Mulliken inner complexes. The consequences of these, as well as of the ultra‐strong interactions, in designing novel functional nanomaterials are outlined. © 2017 Wiley Periodicals, Inc.