arXiv subjects

Jan Kuriplach

Publications and source records attributed to Jan Kuriplach.

3 recordsLinked to original sources

arXiv2019

First-principles study of the impact of grain boundary formation in the cathode material LiFePO4

Motivated by the need to understand the role of internal interfaces in Li migration occurring in Li-ion batteries, a first principles study of a coincident site lattice grain boundary in LiFePO4 cathode material and in its delithiated counterpart FPO4 is performed. The structure of the investigated grain boundary is obtained and the corresponding interface energy is calculated. Other properties, such as ionic charges and magnetic moments, excess free volume and the lifetime of positrons trapped at the interfaces, are determined and discussed. The results show that while the grain boundary in LiFePO4 has desired structural and bonding characteristics, the analogous boundary in FePO4 needs to be yet optimized to allow for an efficient Li diffusion study.

cond-mat.mtrl-sci↗

arXiv2015

Proposed parameter-free model for interpreting the measured positron annihilation spectra of materials using a generalized gradient approximation

Positron annihilation spectroscopy is often used to analyze the local electronic structure of materials of technological interest. Reliable theoretical tools are crucial to interpret the measured spectra. Here, we propose a parameter-free gradient correction scheme for a local-density approximation obtained from high quality quantum Monte Carlo data. The results of our calculations compare favorably with positron affinity and lifetime measurements opening new avenues for highly precise and advanced positron characterization of materials.

cond-mat.mtrl-sci↗

arXiv2014

Improved generalized gradient approximation for positron states in solids

Several first-principles calculations of positron-annihilation characteristics in solids have added gradient corrections to the local-density approximation within the theory by Arponen and Pajanne [Ann. Phys. (N.Y.) 121, 343 (1979)] since this theory systematically overestimates the annihilation rates. As a further remedy we propose to use gradient corrections for other local density approximation schemes based on perturbed hypernetted-chain and on Quantum Monte Carlo results. Our calculations for various metals and semiconductors show that the proposed schemes generally improve the positron lifetimes when they are confronted with experiment. We also compare the resulting positron affinities in solids with data from slow-positron measurements.

cond-mat.mtrl-sci↗