Isotropic negative thermal expansion and its mechanism in tetracyanidoborate salt CuB(CN)4

• Published in: Chinese physics B Vol. 31; no. 6; pp. 66501 - 114
• Main Authors: Wang, Chunyan, Gao, Qilong, Sanson, Andrea, Jia, Yu
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.06.2022; Key Laboratory of Materials Physics of Ministry of Education,International Laboratory for Quantum Functional Materials of Henan,and School of Physics and Microelectronics,Zhengzhou University,Zhengzhou 450052,China; Key Laboratory for Quantum Materials and Center for Topological Functional Materials,Henan University,Kaifeng 475004,China%Key Laboratory of Materials Physics of Ministry of Education,International Laboratory for Quantum Functional Materials of Henan,and School of Physics and Microelectronics,Zhengzhou University,Zhengzhou 450052,China%Department of Physics and Astronomy,University of Padova,Padova I-35131,Italy%Key Laboratory of Special Functional Materials of Ministry of Education,and School of Materials Science and Engineering,Henan University,Kaifeng 475004,China; Key Laboratory of Special Functional Materials of Ministry of Education,and School of Materials Science and Engineering,Henan University,Kaifeng 475004,China; Key Laboratory for Quantum Materials and Center for Topological Functional Materials,Henan University,Kaifeng 475004,China
• Subjects: crystal structure; negative thermal expansion; phonons; Prussian blue analogues; crystal structure; Prussian blue analogues; negative thermal expansion; phonons
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/ac6019

The control of thermal expansion is essential in applications where thermal stability is required from fiber optics coatings, high performance fuel cell cathodes to tooth fillings. Negative thermal expansion (NTE) materials, although rare, are fundamental for this purpose. This work focuses on studying tetracyanidoborate salt CuB(CN) 4 , an interesting cubic-structure material that displays large isotropic NTE. A joint study of synchrotron x-ray diffraction, temperature-dependent Raman spectroscopy, and lattice dynamics calculations was conducted, showing that not only low-frequency optical modes (transverse thermal vibrations of N and C atoms) but also the acoustic modes (the vibrations of Cu atoms as a collective torsion of the neighboring atoms), contribute to NTE. As a result, new insights were gained into the NTE mechanism of CuB(CN) 4 and related framework materials.