Comments welcome via email: <a href="mailto:natalie@wfu.edu"> 
natalie@wfu.edu. </a><br><br>

<h4>
Computational investigation of the structural and electrolyte properties of the extended
family of lithium (thio)boracite materials: Li<sub>4</sub>B<sub>7</sub>O<sub>12</sub>Cl and beyond
</h4>
<p>
   D. Cory Lynch, Yan Li, Pieremanuele Canepa, and N.A.W. Holzwarth<br />
<a href="https://link.aps.org/doi/10.1103/PhysRevMaterials.8.065401">
     Physical Review Materials <b>8 </b>, 065401 (2024) </a> &nbsp;
     Local copy:  <a href="./papers/boraciteextend/PhysRevMaterials.8.065401.pdf">PDF</a> &nbsp;
     Supplemental materials:  <a href="./papers/boraciteextend/SI1.pdf">SI1</a>&nbsp;
                               <a href="./papers/boraciteextend/SI2.pdf">SI2</a><p>


<p>
<hr></p>
Motivated by previous investigations that showed very promising high ionic conductivities
 within relatively stable framework structures, we report a systematic first-principles study of the extended
 family of lithium (thio)boracites, consisting of eight chemical compositions.
 Three of the compositions -- Li<sub>4</sub>B<sub>7</sub>O<sub>12</sub>Cl,  
Li<sub>4</sub>Al<sub>3</sub>B<sub>4</sub>O<sub>12</sub>Cl, and Li<sub>6</sub>B<sub>7</sub>S<sub>13</sub>Cl
-- are comparable to synthesized and analyzed materials reported in the experimental literature.
The five additional compositions  -- Li<sub>4</sub>B<sub>7</sub>S<sub>12</sub>Cl,  
Li<sub>4</sub>Al<sub>3</sub>B<sub>4</sub>S<sub>12</sub>Cl,
Li<sub>6</sub>B<sub>7</sub>O<sub>13</sub>Cl, Li<sub>6</sub>Al<sub>3</sub>B<sub>4</sub>O<sub>13</sub>Cl, 
and Li<sub>6</sub>Al<sub>3</sub>B<sub>4</sub>S<sub>13</sub>Cl
-- are newly predicted from the computational modeling and analysis presented in this work.
For each material, idealized ordered  rhombohedral, cubic, or  monoclinic  ground state structures
are determined.  Through various methodologies including thermodynamic, voltage window, and harmonic phonon analyses,
        stability is assessed for all eight Li (thio)boracite-derived compositions.
        Based on the dominant energetics of density functional
theory, an analysis of the thermodynamically accessible phases  predicts stability for 
Li<sub>4</sub>B<sub>7</sub>O<sub>12</sub>Cl only.
 The analysis of the voltage windows of these materials suggests that
the sulfur materials are much more reactive in contact with lithium metal than their oxygen counterparts.
This reactivity problem has been identified in other highly conducting solid electrolytes and various mitigation
methods discussed in the literature look promising.
Within the harmonic approximation,
 phonon analysis predicts that all eight materials are dynamically stable in their ground state structures.
Future investigations will focus on  the performance of the family of lithium
        (thio)boracites, including ionic conductivity
predictions and
ion migration mechanisms.

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