Crystalline Inorganic Solid Electrolytes: Computer Simulations and Comparisons with Experiment

Johannes, M. D.; Holzwarth, N. A. W.

doi:10.1142/9789814651905_0006

Cited by 2 publications

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References 103 publications

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“…We introduced the "disordered subspace" formalism which calls attention to the fact that as a function of temperature T , a subspace N 0 (T ) of the full S samples and correspondingly N 0 (T ) configurations of the master set Ω contribute to the free energy approximated by Eq. (30). While this approach may or may not be competitive with directly evaluating the sampled canonical partition function through Eq.…”

Section: Discussionmentioning

confidence: 99%

First-principles estimation of partition functions representing disordered lattices such as the cubic phases of Li2OHCl and Li2OHBr

Howard

Holzwarth

2019

Phys. Rev. B

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In order to develop computational methods that can simulate thermodynamic properties of disordered materials at a first principles level, we investigate the use of a random set of configurations to evaluate the canonical partition function of lattice-based disordered systems. Testing the sampling method on the one and two dimensional Ising models indicates that for the ordered system at low temperature, convergence is achieved when the number of samples S is comparable or larger than the number of configurations Ω, while for the partially disordered system at high temperature, convergence is achieved for smaller sample sizes as low as S ≈ Ω/100 or S ≈ Ω/1000. The sampling method is combined with first principles calculations to examine the ordered ↔ disordered phase transition for the Li ion electrolyte materials Li2OHCl and Li2OHBr. Static lattice internal energies and harmonic phonon free energies were incorporated into the evaluation of the partition function. The evaluation of the partition function depends on the value of Ω corresponding to the number of metastable states of the system. Accordingly, we developed a method of approximating Ω using the properties of the sampled configurations. The results of the calculations are consistent with the experimental observation that the transition temperature for the orthorhombic ↔ cubic phase transition is higher for Li2OHCl than for Li2OHBr. We expect the sampling method to be generally useful for investigating the thermodynamic properties of other disordered lattice systems. We also investigate a "disordered subspace function" which is shown to satisfy inequality relationships with respect to the Helmholtz free energy.

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Section: Discussionmentioning

confidence: 99%

First-principles estimation of partition functions representing disordered lattices such as the cubic phases of Li2OHCl and Li2OHBr

Howard

Holzwarth

2019

Phys. Rev. B

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Ion dynamics in solid electrolytes for lithium batteries

et al. 2017

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All-solid-state batteries with ceramic electrolytes and lithium metal anodes represent an attractive alternative to conventional ion battery systems. Conventional batteries still rely on flammable liquids as electronic insulators. Despite the great efforts reported over the last years, the optimum solid electrolyte has, however, not been found yet. One of the most important properties which decides whether a ceramic is useful to work as electrolyte is ionic transport. The various time-domain nuclear magnetic resonance (NMR) techniques might help characterize and select the most suitable candidates. Together with conductivity measurements it is possible to analyze ion dynamics on different length-scales, i.e., to differentiate between local, within-site hopping processes from long-range ion transport. The latter needs to be sufficiently fast in the ceramic, in the best case competing with that of liquid electrolytes. In addition to conductivity spectroscopy, NMR can help understand the relationship between local structure and dynamic parameters. Besides information on activation energies and jump rates the data also contain suggestions about the relevant elementary steps of ion hopping and, thus, Support by the Deutsche Forschungsgemeinschaft (DFG) is highly appreciated (FOR 1277 diffusion pathways through the crystal lattice. Recent progress in characterizing ion dynamics in ceramic electrolytes by NMR relaxometry will be briefly reviewed. Focus is put on presently discussed solid electrolytes such as garnets, phosphates and sulfides, which have so far been studied in our lab.

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Crystalline Inorganic Solid Electrolytes: Computer Simulations and Comparisons with Experiment

Cited by 2 publications

References 103 publications

First-principles estimation of partition functions representing disordered lattices such as the cubic phases of Li2OHCl and Li2OHBr

First-principles estimation of partition functions representing disordered lattices such as the cubic phases of Li2OHCl and Li2OHBr

Ion dynamics in solid electrolytes for lithium batteries

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