Abstract
Prediction of structural phase of transition metal composites is highly required because the electronic and magnetic properties are deeply related to the crystal structures. The d-orbital occupancy has been suggested as a simple descriptor to predict the structural phase of transition metal composition in nonmagnetic ground state. In this work, we suggest new rule, orbital-spin occupancy rule with new descriptor nd-σd (σd is spin moment.) to predict stable crystal structure, which should be generally applied to nonmagnetic as well as magnetic system. Using first-principles calculation, we show that all 3d, 4d, and 5d transition metals follow this rule. Also, we confirm that structural phase can be controlled by changing nd-σd with pressure and electron doping. We suggest that orbital-spin occupancy rule should be widely applied to the prediction of various transition metal composites.
Highlights
Physical and chemical properties of solids depend on their crystal structures
Magnetic properties of materials are sensitive to their crystal structures, which are attributed to the structural dependence of the spin states,[1,2] it is important to predict a stable crystal structure of materials for designing of functional materials such as strong permanent magnet
One electron band theory predicted that most 3d, 4d, and 5d transition metals follow the same trend of changing the structural phases from hcp, bcc, hcp to fcc as increasing d-orbital occupancy, from 0 to 10.4–6 Later it was extended to investigate the stability of 6d transition metal[7] and applied to the solubility of transition metal alloy.[8]
Summary
Physical and chemical properties of solids depend on their crystal structures. For example, magnetic properties of materials are sensitive to their crystal structures, which are attributed to the structural dependence of the spin states,[1,2] it is important to predict a stable crystal structure of materials for designing of functional materials such as strong permanent magnet. Density functional theory (DFT) has been successful to predict the crystal structures of new materials based on evolutionary algorithms.[3] it still demands a lot of computational costs about a new compound which consists of a lot of atoms. It is very useful for finding stable crystal structure if there is a simple rule based on a descriptor which can be obtained. The stability of various crystals (simple metal, transition metal, and light actinide) were determined by the bandwidth of valence electron states,[12] but this work has not been extended to predict stable structure of magnetic materials. It is shown that nd-σd determines the structural phase of transition metals under pressure and electron doping, which can be extended to the prediction of transition metal alloys under various condition
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