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Open AccessArticle

A First-Principles Exploration of NaxSy Binary Phases at 1 atm and Under Pressure

1
Department of Chemistry, University at Buffalo, Buffalo, NY 14260, USA
2
School of Sciences, Changchun University, Changchun 130022, China
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(9), 441; https://doi.org/10.3390/cryst9090441
Received: 1 August 2019 / Revised: 19 August 2019 / Accepted: 20 August 2019 / Published: 24 August 2019
(This article belongs to the Special Issue First-Principles Prediction of Structures and Properties in Crystals)
Interest in Na-S compounds stems from their use in battery materials at 1 atm, as well as the potential for superconductivity under pressure. Evolutionary structure searches coupled with Density Functional Theory calculations were employed to predict stable and low-lying metastable phases of sodium poor and sodium rich sulfides at 1 atm and within 100–200 GPa. At ambient pressures, four new stable or metastable phases with unbranched sulfur motifs were predicted: Na2S3 with C 2 / c and Imm2 symmetry, C 2 -Na2S5 and C 2 -Na2S8. Van der Waals interactions were shown to affect the energy ordering of various polymorphs. At high pressure, several novel phases that contained a wide variety of zero-, one-, and two-dimensional sulfur motifs were predicted, and their electronic structures and bonding were analyzed. At 200 GPa, P 4 / m m m -Na2S8 was predicted to become superconducting below 15.5 K, which is close to results previously obtained for the β -Po phase of elemental sulfur. The structures of the most stable M3S and M4S, M = Na, phases differed from those previously reported for compounds with M = H, Li, K. View Full-Text
Keywords: high-pressure; crystal structure prediction; electronic structure; battery materials; superconductivity high-pressure; crystal structure prediction; electronic structure; battery materials; superconductivity
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MDPI and ACS Style

Geng, N.; Bi, T.; Zarifi, N.; Yan, Y.; Zurek, E. A First-Principles Exploration of NaxSy Binary Phases at 1 atm and Under Pressure. Crystals 2019, 9, 441.

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