Large negative thermal expansion in GdFe(CN)_(6) driven by unusual low-frequency modes

查看全文 作　　者：Qilong [1]Gao;Yixin [1]Jiao;Andrea [2]Sanson;Erjun [1]Liang;Qiang [1]Sun 机构地区：[1]Key Laboratory of Materials Physics of Ministry of Education,and School of Physics and Microelectronics,Zhengzhou University,Zhengzhou 450052,China;[2]Department of Physics and Astronomy,University of Padova,Padova I-35131,Italy 出　　处：《Chinese Chemical Letters》索引2023年第34卷第5期,共4页 基　　金：supported by the National Natural Science Foundation of China(Nos.22071221 and 21905252);the Natural Science Foundation of Henan Province(No.212300410086);Use of the Advanced Photon Source,an Office of Science User Facility operated for the U.S.Department of Energy(DOE)Office of Science by Argonne National Laboratory,was supported by the U.S.DOE under Contract No.DE-AC02-06CH11357。 摘　　要：Understanding the negative thermal expansion(NTE)mechanism is of great importance.In this work,we consider the new NTE compound Gd Fe(CN)_(6)(α_(v)=-34.2×10^(-6)K^(-1))as a case study to investigate the NTE mechanism from the perspective of the lattice vibrational dynamics.The atomic mean-square displacements suggest that the NTE of Gd Fe(CN)_(6)comes from the strong tension effect induced by the transverse vibrations of the atomic-Fe-C≡N-Gd-linkages,with the largest contribution given by N atoms.Lattice dynamics calculations show that three low-frequency optical modes at about 50 cm^(-1)show the largest negative Grüneisen parameters thus providing the largest contribution to the NTE.The existence of these unusual low-frequency vibrational modes can be ascribed to the presence of GdN_(6)trigonal prisms in the framework structure of Gd Fe(CN)_(6). 关 键 词：Negative thermal expansion Prussian blue analogues Low frequency phonon Crystal structure Transverse vibration