Abstract Mercurous halide single crystals with one-dimensional chain-like structure exhibit great potential as polarizers or acousto-optic devices in infrared range based on the ultra-large birefringence and ultra-wide infrared transmission range. However, the origin of these two unique properties of mercurous halide families are unclear. Herein, we theoretically investigate the electronic and vibrational properties of these analogues through first principle calculation to explore the origin of these two distinct properties. The short cut-on wavelength is due to the large bandgap stemming from the ability of halogen to bind valence electrons tightly, while the long wavelength infrared cut-off originates from low phonon frequency caused by the high atomic weight of Hg and halogen atoms. Attributed to the high covalent characteristic between Hg and halogen atoms along c orientation and the very weak van der Waals force between X-Hg-Hg-X (X = Cl, Br, I) molecules perpendicular to c orientation, mercurous halide crystals exhibit large anisotropy of polarization leading to the large birefringence. Our analysis reveals that both one-dimensional chain structure and high atomic number elements contribute to the large birefringence and wide infrared transparent range, which would inspire a direction for designing new high-performance infrared polarizing materials.

中文翻译：

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具有一维链状结构的卤化汞系列的超宽红外透射和超大双折射的起源：从头开始的研究

摘要 具有一维链状结构的卤化亚汞单晶基于超大双折射和超宽红外传输范围，在红外范围内具有作为偏振器或声光器件的巨大潜力。然而，卤化亚汞家族的这两种独特性质的起源尚不清楚。在这里，我们通过第一性原理计算从理论上研究了这些类似物的电子和振动特性，以探索这两种不同特性的起源。短截止波长是由于卤素与价电子紧密结合的能力产生的大带隙，而长波长红外截止波长是由于汞和卤素原子的高原子量引起的低声子频率。由于 Hg 和卤素原子之间沿 c 取向的高共价特性和垂直于 c 取向的 X-Hg-Hg-X (X = Cl, Br, I) 分子之间非常弱的范德华力，卤化汞晶体表现出大偏振的各向异性导致大的双折射。我们的分析表明，一维链结构和高原子序数元素都有助于大双折射和宽红外透明范围，这将为设计新型高性能红外偏振材料提供一个方向。