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

Crystals

Niloofar Zarifi¹  Eva Zurek¹  Yan Yan¹  Nisha Geng¹  Tiange Bi¹ 

[1] Department of Chemistry, University at Buffalo, Buffalo, NY 14260, USA;

关键词: high-pressure;    crystal structure prediction;    electronic structure;    battery materials;    superconductivity;   

DOI  :  10.3390/cryst9090441

来源: DOAJ

【 摘 要 】

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 $C2/c$ and Imm2 symmetry, $C2$ -Na₂S₅ and $C2$ -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, $P4/mmm$ -Na₂S₈ was predicted to become superconducting below 15.5 K, which is close to results previously obtained for the $\beta$ -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.

【 授权许可】

Unknown