Quantum-chemical prediction and computational characterization of high-pressure transitionmetal nitrides and oxynitrides

点击翻译按钮获取中文摘要

The purpose of this theoretical project is to predict, by means of various quantum-chemical techniques, the existence of a number of novel nitridic and also oxynitridic compounds which are only accessible by using extreme synthetic pressures but not using ordinary experimental methods. We will accomplish this goal by utilizing a number of ab initio computational strategies, and we will closely interact with the experimentally working groups of Rainer Niewa (MPI Dresden, soon TU München) and Ulrich Schwarz (MPI Dresden). In particular, we will perform total-energy calculations for hypothetical and stoichiometrically reasonable transition-metal nitrides and oxynitrides, and we will computationally analyze their thermochemical stabilities with respect to competing (educt) phases prior to synthesis, namely by simulating their high-pressure behavior at different pressures up to 100 GPa in the form of ab initio energy¿volume and enthalpy¿pressure diagrams. This gives access to theoretical phase-transition pressures and even to formation pressures provided that all reactants are solid-state materials. The parameter temperature will be introduced using a simple approximation, thereby yielding pressure¿temperature diagrams which will allow our experimental partners to easily extract the optimum synthetic pressures and temperature ranges even if gaseous reactants should be involved. In particular, we will theoretically predict potentially stable binary transition-metal/platinum-group nitrides, quaternary nitrides (M,M¿)Fe3N incorporating different iron- and platinum-group metals, as well as daltonide and berthollide oxynitrides ¿MON¿ with M being chromium, manganese, and iron. Eventually, we will assist our synthetic partners in identifying and analyzing their synthesized materials with respect to the structure type found, atomic-site parameters, atomic distributions, prediction of physical properties and, especially, the bonding situation via DOS and COHP analyses.