One-for-multiple substitution in solid solutions

TL;DR

This study reveals that large solute atoms can replace multiple atoms in beryllium's crystal lattice, challenging the traditional one-for-one substitution assumption and impacting solubility and material properties.

Contribution

It demonstrates through first-principles calculations that large solutes can substitute multiple atoms in a crystal, providing new insights into solid solution behavior.

Findings

Cr substitutes for one atom, V and Mo for three, others for four or five.

Zr, Hf, Sc, Y have exothermic dissolution, indicating good solubility.

Sc shows potential to enhance superplasticity in Be.

Abstract

It is generally assumed that one solute atom will occupy only one lattice site in a substitutional solid solution. We here report an interesting discovery by first-principles calculations that a large solute atom can replace multiple matrix atoms in the elemental crystal of beryllium. Examination on Groups IIIB, IVB, VB, VIB, and VA elements shows that Cr will substitute for one, V and Mo for three, Sc, Y, Ti, Zr, Hf, W, Nb, Ta, As, Sb, and Bi for four, and La for five Be atoms. Dissolution of Zr, Hf, Sc, and Y is exothermic, suggesting a good solubility. At low concentration, the configurational entropy resulted from one-for-multiple substitution is larger than in the one-for-one substitution case. We find that Sc, Y, Zr, and Hf all have tendency to aggregate in Be, but Sc is the weakest among them and thus can be expected to improve the superplasticity of Be.