Comments welcome via email:
natalie@wfu.edu.
Computational and experimental (re)investigation of the structural
and electrolyte properties of
Li4P2S6, and
Na4P2S6, and
Li2Na2P2S6
Yan Li, Zachary D. Hood,
and N.A.W. Holzwarth
Physical Review Materials 4 , 045406 (2020)
Local copy
The ionic materials Li4P2S6 and
Na4P2S6
are both based on the same building blocks of the dimer ions
(P2S64- )
Motivated by new experimental structural and ion conductivity studies,
we computationally examine
this family of materials, finding Na4P2S6
and its modification Li2Na2P2S6
to be promising Na ion electrolytes.
Using first-principles calculations based on density functional theory and
density functional perturbation theory
within the harmonic phonon approximation, we show that vibrational
effects provide nontrivial contributions to
the structural stabilization of these materials. Computed nonresonant
Raman phonon spectra and temperature dependent ionic conductivity for
Na4P2S6 are both found to be in
reasonable agreement with experiment.
First-principles analysis of ionic conductivity in both
Na4P2S6 and
Li2Na2P2S6
indicates that Na ions move
primarily within the interlayer region between the (P2S64- )
layers, efficiently proceeding via direct or indirect
hops between vacancy sites, with indirect processes involving intermediate
interstitial sites.