Complex lithium ion dynamics in simulated LiPO3 glass studied by means of multitime correlation functions

Article

关键词: IONICALLY CONDUCTING GLASSES;    ALKALI METAPHOSPHATE GLASSES;    2-DIMENSIONAL AG-109 NMR;    MOLECULAR-DYNAMICS;    PHOSPHATE-GLASSES;    SILICATE-GLASSES;    SILVER DYNAMICS;    ELECTRICAL RELAXATION;    COMPUTER-SIMULATION;    DECAY FUNCTION;   

DOI  :  10.1103/PhysRevB.68.184301

来源: SCIE

【 摘 要 】

Molecular dynamics simulations are performed to study the lithium jumps in LiPO3 glass. In particular, we calculate higher-order correlation functions that probe the positions of single lithium ions at several times. Three-time correlation functions show that the nonexponential relaxation of the lithium ions results from both correlated back-and-forth jumps and the existence of dynamical heterogeneities, i.e., the presence of a broad distribution of jump rates. A quantitative analysis yields that the contribution of the dynamical heterogeneities to the nonexponential depopulation of the lithium sites increases upon cooling. Further, correlated back-and-forth jumps between neighboring sites are observed for the fast ions of the distribution, but not for the slow ions and, hence, the back-jump probability depends on the dynamical state. Four-time correlation functions indicate that an exchange between fast and slow ions takes place on the time scale of the jumps themselves; i.e., the dynamical heterogeneities are short lived. Hence, sites featuring fast and slow lithium dynamics, respectively, are intimately mixed. In addition, a backward correlation beyond the first neighbor shell for highly mobile ions and the presence of long-range dynamical heterogeneities suggest that fast ion migration occurs along preferential pathways in the glassy matrix. In the melt, we find no evidence for correlated back-and-forth motions and dynamical heterogeneities on the length scale of the next-neighbor distance.

【 授权许可】

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