New Quasicrystal Approximant in the Sc–Pd System: From Topological Data Mining to the Bench

Pavlo Solokha,Albina Gurskaya,Tilmann Leisegang,Serena De Negri,Davide M Proserpio,Tatiana Akhmetshina,Roman A Eremin,Adriana Saccone

doi:10.1021/acs.chemmater.9b03767

Abstract

Intermetallics contribute significantly to our current demand for high-performance functional materials. However, understanding their chemistry is still an open and debated topic, especially for complex compounds such as approximants and quasicrystals. In this work, targeted topological data mining succeeded in (i) selecting all known Mackay-type approximants, (ii) uncovering the most important geometrical and chemical factors involved in their formation, and (iii) guiding the experimental work to obtain a new binary Sc–Pd 1/1 approximant for icosahedral quasicrystals containing the desired cluster. Single-crystal X-ray diffraction data analysis supplemented by electron density reconstruction using the maximum entropy method, showed fine structural peculiarities, that is, smeared electron densities in correspondence to some crystallographic sites. These characteristics have been studied through a comprehensive density functional theory modeling based on the combination of point defects such as vacancies a...

Highlights

Chemistry of intermetallics is still one of the most complicated topics in materials science, mainly because of their strong and almost continuous variation with the composition and nature of the elements involved
Rational Mackay approximant crystals (ACs) Known up to Date. When this investigation was started on the occasion of Alan Mackay’s 90th birthday,[29] a curiosity arose how one can find a group of compounds with a certain structure characteristic such as a Mackay-type cluster within the ever-growing databases? Statistical data elaboration based on symmetry properties, such as space group, Pearson symbol, lattice parameters, and standardized representations[55] may help to some extent,[1] but it is known that among intermetallics, frequently, structural relations exist between chemically different systems with different numbers of atoms in the unit cell, different sets of Wyckoff sequences, and different space groups
The manifold approaches applied in this study show that the topologically based screening is extremely useful in the design of new materials

Summary

Introduction

Chemistry of intermetallics is still one of the most complicated topics in materials science, mainly because of their strong and almost continuous variation with the composition and nature of the elements involved. Compounds formed by two or more metals exhibit a wide structural diversity, which is the origin of many difficulties in their description and classification. According to the crystallographic data analysis of Dshemuchadse and Steurer,[1] among 20,829 intermetallics (involving 81 elements of the periodic table) crystallizing in 2166 different structure types, almost 2% of the structures exhibit more than 100 atoms per unit cell and are termed “complex intermetallics” (CIMs). The convenience and logic of the cluster representation of complex structures is obvious: intermetallics with more than a thousand[2,3] or even tens of thousands[4,5] of atoms per unit cell look much simpler when represented as cluster assemblages. The physical significance of such a description and the definition of the clusters themselves[6] still remains an open challenge

Methods

Results

Conclusion