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Anharmonic properties of Prussian blue analogues MIIPtIV(CN)6 (MII = Cd, Fe, Zn)
Geng Wang1, Zhi-Hao Yao2, Ken Suzuki3
1Department of Physics, Institute of Theoretical Physics, University of Science and Technology Beijing, Beijing 100083, China. leiw_phy@ustb.edu.cn.
Abstract:
This work investigates the anharmonic properties of MIIPtIV(CN)6 (MII = Cd, Fe, Zn) based on three-phonon interactions. The results demonstrate that FePt(CN)6 exhibits higher lattice thermal conductivity (LTC) with greater tunability. In all three crystals, the scattering rate decreases with increasing boundary mean free path (MFP), and within each crystal, low-frequency phonons exhibit higher scattering rates than high-frequency ones. The phonon lifetime decreases with rising temperature, with an anomalously long lifetime observed around 67 THz. It is observed that all three crystals exhibit notably negative mode-Grüneisen parameters in the low-frequency region, highlighting the dominant contribution of low-frequency phonons to negative thermal expansion (NTE). Furthermore, the recombination process prevails in the low-frequency region of the three crystals, which can be seen from the joint density of states (JDOS) plots. In the weighted joint density of states (w-JDOS) plots, CdPt(CN)6 and ZnPt(CN)6 exhibit an alternating pattern of recombination and decay processes at low frequencies, and FePt(CN)6 exhibits the fewest scattering channels. The phonon branches of FePt(CN)6 exhibit pronounced dispersion, which correlates with its higher LTC.
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