Electron Density Studies in Materials Research

Abstract

Rational material design requires a deep understanding about the relationship between the structure and properties of materials, which are both intimately related to their chemical bonding. Through the experimentally observable electron density, chemical bonding can be understood from experimental and theoretical points of view on an equal footing, and advances in accurate X‐ray diffraction measurements and computational techniques over the past decades have provided access to electron density distributions in increasingly complex functional materials. In this Review, selected electron density studies from the literature on a wide range of materials classes are presented, including studies of thermoelectric materials, high pressure electrides, coordination polymers and non‐linear optical materials. These studies demonstrate how detailed analysis of chemical bonding based on the electron density provides important understanding of materials beyond arguments based on structure and simple chemical concepts. In cases such as understanding the conducting properties of Zintl semiconductors or the effect of mutual electrical polarization in host–guest systems, it is clearly imperative to go beyond structure and examine the chemical bonding in detail. In the Review, the complementarity between theory and experiment is underlined, which allows for mutual validation of new chemical bonding concepts, and indeed experiment and theory may challenge each other based on the different strengths and weaknesses of each method.

A Theoretical Investigation on Chemical Bonding of the Bridged Hydride Triruthenium Cluster: [Ru3 (μ-H)( μ3-κ2-Hamphox-N,N)(CO)9]

“…The important development in the topological analysis, specifically, the atoms in molecules (AIM) theory which developed by Bader and his group, is to study both experimental and theoretical electron density distributions. Additionally, this approach provides a useful tool for studying various interactions in a molecular system (12)(13)(14)(15)(16)(17).…”

Chemical Bonding in Colossal Thermopower FeSb2

“…So far,n oX -ray electrond ensity (ED) analysish as been attempted to providee xperimental evidencef or the electronic structure. [8][9][10] As the ED imparts the physical properties of a system, it is clearlyi mportant to provide an understanding of the specific chemicalb onding and atomic valences tates in FeSb 2 .H owever,t he study of FeSb 2 by X-ray ED analysis is a great challenge becausethe structure contains heavya toms,i n whicht he valence electrons only contribute weakly to the diffractedi ntensities. An X-ray ED study of the similarly challenging thermoelectric material CoSb 3 has been reported [11,12] with as uitability factor, S ¼ V= P i;unit cell n 2 core;i , [13] of 0.01, which is much lower than the values of 5-10 typically seen for organic compounds.…”

“…The origin of the extraordinary temperature dependence of the transport properties has been heavily debated, and theoretical and experimental data suggest that they are linked to a combination of phonon‐drag, electron‐correlation effects, and anti‐site defects to generate impurity in‐gap electronic states. So far, no X‐ray electron density (ED) analysis has been attempted to provide experimental evidence for the electronic structure . As the ED imparts the physical properties of a system, it is clearly important to provide an understanding of the specific chemical bonding and atomic valence states in FeSb 2 .…”

Topological analysis of chemical bonding in the layered FePSe3 upon pressure‐induced phase transitions

“…[1,2] Due to the progress in quantum chemistry calculations, the method has gained popularity and finds numerous applications in studies of organic and inorganic compounds. [3][4][5][6][7][8][9][10][11][12][13][14][15] In particular, the method helps to identify changes in chemical bonds and mechanisms of phase transitions under high pressure. [16][17][18][19][20][21][22][23][24][25][26] At the same time, the use of topological analysis for the understanding of bonding in layered compounds is not numerous.…”