Tunable Thermal Expansion from Negative, Zero, to Positive in Cubic Prussian Blue Analogues of GaFe(CN)₆

Abstract

The achievement of controlling thermal expansion is important for open-framework structures. The present work proposes a feasible way to adjust the coefficient of thermal expansion continuously from negative to positive via inserting guest Na + ions or H 2 O molecules into a GaFe(CN) 6 framework. The guest ions or molecules have an intense dampening effect on the transverse vibrations of CN atoms in the −Ga−NC− Fe− linkage, especially for the N atoms. This study demonstrates that electrochemical or redox intercalation of guest ions will be an effective way to tune thermal expansion in those negative thermal expansion openframework materials induced by low-frequency phonons.

First Principles Study on the Effect of Pressure on the Structure, Elasticity, and Magnetic Properties of Cubic GaFe(CN)6 Prussian Blue Analogue

“…In the structure of GaFe(CN)6, the -Ga-N≡C-Fe-chain is formed between gallium, carbon, nitrogen, and iron atoms. Experimentally, the lattice constant of GaFe(CN)6 was measured as 10.0641 Å at 273 K [36], and the occupied positions of each atom in the structure are shown in Table 1. In order to obtain the theoretical equilibrium lattice constant and the ground state properties of GaFe(CN) 6 , we constructed supercells based on experimental structural parameters and calculated the total energy of ferromagnetic (FM), non-magnetic (NM), and antiferromagnetic (AFM) states of GaFe(CN) 6 under different lattice constants.…”

“…In Prussian blue analogs, there is a large space between metal ions and -CN-groups, which can effectively accommodate alkali metal ions such as Li + , Na + , and K + . The open structure of Prussian blue analogs makes it exhibit excellent electrochemical performance [35][36][37].…”

EXAFS spectroscopy: a powerful tool for the study of local vibrational dynamics

“…Very interesting is the fact that the insertion of guest ions or molecules in PBA structures can inhibit NTE, thereby opening the possibility of controlling the thermal expansion of materials. For examples, the incorporation of K + ions or H 2 O molecules in YFe(CN) 6 switches its thermal expansion from strongly negative to strongly positive [116] , while the progressive insertion of Na + ions in GaFe(CN) 6 changes the thermal expansion from negative to zero to positive [117] . In addition, the intercalation of H 2 O molecules in TiCo(CN) 6 changes the thermal expansion from negative to zero below room temperature [118] .…”

“…EXAFS was used to study superconducting materials. Lanzara et al [119] studied the local atomic correlations in the HgBa [117,118] . © ACS Publishing.…”

“…The effect is much more pronounced for the M-N bonds than for the M'-C bonds. Figure taken from Refs [117,118]. .…”