一种新的常压超导开骨架硅同素异形体
A new superconducting open-framework allotrope of silicon at ambient pressure
摘要：
金刚石硅是一种具有间接带隙的半导体，是现代半导体技术的基础。虽然许多亚稳态形式的硅被观察到使用金刚石压砧单元的压缩和化学前体的合成，在环境条件下没有金属相迄今已被报道。在这里，我们报告的预测纯金属硅同素异形体在环境压力下的开放通道，不像一个立方金刚石结构的共价键网络。通过高压下的第一性原理研究发现了一种新型的Na-Si包合物P6/m-NaSi 6，在高压下减压脱Na后可以得到金属相P6/m-Si 6。我们证实了P6/m-NaSi 6和P6/m-Si 6是稳定的超导体，在常压下的临界温度分别为13和12 K。新的Na-Si和Si笼形结构的发现提出了探索用于Si基器件的新的外来同素异形体的可能性。
英文摘要：
Diamond Si is a semiconductor with an indirect band gap that is the basis of modern semiconductor technology. Although many metastable forms of Si were observed using diamond anvil cells for compression and chemical precursors for synthesis, no metallic phase at ambient conditions has been reported thus far. Here we report the prediction of pure metallic Si allotropes with open channels at ambient pressure, unlike a cubic diamond structure in covalent bonding networks. The metallic phase termed P6/m-Si6 can be obtained by removing Na after pressure release from a novel Na-Si clathrate called P6/m-NaSi6, which is discovered through first-principles study at high pressure. We confirm that both P6/m-NaSi6 and P6/m-Si6 are stable and superconducting with the critical temperatures of about 13 and 12 K at ambient pressure, respectively. The discovery of new Na-Si and Si clathrate structures presents the possibility of exploring new exotic allotropes useful for Si-based devices.
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