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natalie@wfu.edu.
First principles investigation of the Structural and electrolyte properties of
Na4P2S6 and
Li4P2S6
Larry E. Rush Jr.
and N.A.W. Holzwarth
Solid State Ionics 286, 45-50 (2016)
Local copy
First principles simulations are used to examine the structural and
physical properties of Na4P2S6 in
comparison with its
Li4P2S6 analog.
Four model structures are considered including
the C2/m structure recently reported by Kuhn and co-workers from
their analysis of single crystals of Na4P2S6,
and three
structures related to
the P63/mcm structure with P site disorder found in 1982 by
Mercier and co-workers from their analysis of single crystals
of Li4P2S6.
The computational results indicate that
both Na4P2S6 and
Li4P2S6 have the same
disordered ground
state structures consistent with the P63/mcm space group,
while the optimized
C2/m structures have higher energies
by 0.1~eV and 0.4~eV per formula unit
for Na4P2S6 and
Li4P2S6, respectively.
In modeling ionic conductivity in these materials,
activation energies for Na ion
vacancy migration were computed to be
smaller than the Li analogs in
all of the structural models.
Interestingly, the results also indicate that if
Li4P2S6
Interestingly, the results also indicate that if
Li4P2S6
could be prepared in the meta-stable C2/m structure, the
Li ion vacancy migration would have very small barriers along
certain channels.
Simulations of Na4P2S6(C2/m)/Na
interfaces indicate that they
may be
slightly less reactive than
Li4P2S6(P63/mcm)/Li
interfaces.