Rutile-mimic 3D metamaterials with simultaneously negative Poisson's ratio and negative compressibility

The origin of negative Poisson's ratio in rutile-type oxides and fluorides is explored through density functional theory (DFT) simulation. The study highlights the dominant role of nearest-neighbor central force interactions, thereby inspiring the design of a new three-dimensional (3D) mechanical metamaterial by mimicking the bond structure via elastic beams. Analytical expressions for the effective Poisson's ratio and compressibility are derived and validated by finite element computations. Numerical results indicate that the material can exhibit simultaneously negative Poisson's ratio and negative linear, area, or volume compressibility. The negative Poisson's ratio is conformed experimentally, and the parametric spaces leading to negative compressibilities are identified explicitly. (c) 2020 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The study explores the origin of negative Poisson's ratio in rutile-type oxides and fluorides through density functional theory (DFT) simulation, highlighting the dominant role of nearest-neighbor central force interactions. A new three-dimensional mechanical metamaterial is designed by mimicking the bond structure via elastic beams. The analytical expressions for the effective Poisson's ratio and compressibility are derived and validated by finite element computations, indicating the material can exhibit negative Poisson's ratio and negative linear, area, or volume compressibility simultaneously.