Work

Planar negative thermal expansion in the layered hybrid network material ZnB 2 ( CN ) 8

Year: 2025

Type: article

Abstract: We report a computational study of thermal expansion in the hybrid layer structure ZnB 2 ( CN ) 8 using density functional theory (DFT) methods. The crystal structure has a trigonal lattice, with a larger positive thermal expansion in the axial direction ( c axis) and a very small negative thermal expansion within the layer normal to the axial axis (the a − b plane). The results of the DFT calculations for the structure, lattice dynamics and thermal expansion are consistent with experimental data, and, together with a flexibility analysis, it is possible to explain the large difference between axial and area thermal expansivities. We argue from some general features that the difference between the two expansivities is an inevitable consequence of a combination of the elasticity being stiffer within the layers than between the layers, and of the existence of a tension effect operating within the layers, which lowers the values of the area-strain Grüneisen parameters relative to the axial ones. These two factors combine in a way to enhance the axial expansivity but cancel in the calculation of the area expansivity. This is likely to be a general case for any layer structure in which the layers can be described as a partly flexible network.

Source: Physical review. B./Physical review. B

DOI: 10.1103/gc3b-h3c2

Authors: Junbiao Guo, Guanqun Cai, Kaiyue Zhao, Ben Durham, Keith Refson, Martin T Dove

Institutions: Sichuan University, Zhengzhou University, University of York, Science and Technology Facilities Council, Queen Mary University of London

Language: English

Topic: Thermal Expansion and Ionic Conductivity

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: hybrid

Funders: Brigham Young University, National Natural Science Foundation of China

Award: G3837078805