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 mech...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).展开更多
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。
文摘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).
