2022/10/17 by Sajan Kumar, S. Kumar, Kumar, Sajan +22
Chemistry · Engineering · Materials Science · Physics and Astronomy · #Advanced Battery Materials and Technologies #Advancements in Battery Materials #Amorphous solid #Anharmonicity #Chemical physics #Chemistry #Computational chemistry #Condensed matter physics #Crystallography #Diffusion #FOS: Physical sciences #Inelastic neutron scattering #Materials Science (cond-mat.mtrl-sci) #Materials science #Molecular dynamics #Molecular physics #Molecular vibration #Neutron scattering #Nuclear materials and radiation effects #Optics #Phase (matter) #Physics #Quasielastic neutron scattering #Raman spectroscopy #Scattering #Thermodynamics #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.2210.09003
published in arXiv (Cornell University) (Cornell University) · 31 pages, 7 Figures, Supplementary Materials
arxiv created 2022/10/17 · openalex publication_date 2022/10/17 · arxiv updated 2022/10/18 · openalex created_date 2022/10/20 · openalex updated_date 2026/08/08
We present the investigations on atomic dynamics and Li+ diffusion in crystalline and amorphous Li2Si2O5 using quasielastic (QENS) and inelastic neutron scattering (INS) studies supplemented by ab-initio molecular dynamics simulations (AIMD). The QENS measurements in the amorphous phase of Li2Si2O5 show a narrow temperature window (700 < T < 775 K), exhibiting significant quasielastic broadening corresponding to the fast Li+ diffusion and relaxation of SiO4 units to the crystalline phase. Our INS measurements clearly show the presence of large phonon density of states (PDOS) at low energy (low-E) in the superionic amorphous phase, which disappear in the non-superionic crystalline phase, corroborating the role of low-E modes in Li+ diffusion. The frustrated energy landscape and host flexibility (due to random orientation and vibrational motion of SiO4 polyhedral units) play an essential role in diffusing the Li+. We used AIMD simulations to identify that these low-E modes involve a large amplitude of Li vibrations coupled with SiO4 vibrations in the amorphous phase. At elevated temperatures, these vibrational dynamics accelerate the Li+ diffusion via a paddle-wheel like coupling mechanism. Above 775 K, these SiO4 vibrational dynamics drive the system into the crystalline phase by locking SiO4 and Li+ into deeper minima of the free energy landscape and disappear in the crystalline phase. Both experiments and simulations provide valuable information about the atomic level stochastic and vibrational dynamics in Li2Si2O5 and their role in Li+ diffusion and vitrification.