Metastability relationship between two- and three-dimensional crystal structures: a case study of the Cu-based compounds

Shota Ono

doi:10.1038/s41598-021-94034-6

Abstract

Some of the three-dimensional (3D) crystal structures are constructed by stacking two-dimensional (2D) layers. To study whether this geometric concept, i.e., using 2D layers as building blocks for 3D structures, can be applied to computational materials design, we theoretically investigate the dynamical stability of copper-based compounds CuX (a metallic element X) in the B_h and L1_1 structures constructed from the buckled honeycomb (BHC) structure and in the B2 and L1_0 structures constructed from the buckled square (BSQ) structure. We demonstrate that (i) if CuX in the BHC structure is dynamically stable, those in the B_h and L1_1 structures are also stable. Using molecular dynamics simulations, we particularly show that CuAu in the B_h and L1_1 structures withstand temperatures as high as 1000 K. Although the interrelationship of the metastability between the BSQ and the 3D structures (B2 and L1_0) is not clear, we find that (ii) if CuX in the B2 (L1_0) structure is dynamically stable, that in the L1_0 (B2) is unstable. This is rationalized by the tetragonal Bain path calculations.

Highlights

Since the synthesis of many atomically thin materials, the two-dimensional (2D) structure has been regarded as one of the metastable structures in materials science, as a result of which the database including several 2D structures can be available[1,2,3,4,5]
This indicates that the buckled honeycomb (BHC) structure serves as a building block for the B h and L11 structures, while in some compounds the dynamical stability of the B h and L11 structures relies on the coupling between the BHC structures along the c axis
We study the dynamical stability of CuX in the the buckled square (BSQ), B2, and L10 structures, where the latter two structures can be constructed by stacking the BSQ structures

Summary

Introduction

Since the synthesis of many atomically thin materials, the two-dimensional (2D) structure has been regarded as one of the metastable structures in materials science, as a result of which the database including several 2D structures can be available[1,2,3,4,5]. We investigate the interrelationship of the dynamical stability between the 2D and the 3D structures by focusing on CuX with a metallic element X. By calculating the phonon density-of-states (DOS) from first principles, we demonstrate that if CuX in the BHC structure is dynamically stable, CuX in the B h and L11 structures are stable.

Results

Conclusion