二维冰相Ⅰ的电子和光学性质

Electronic and optical properties of two-dimensional ice Ⅰ

二维冰是典型的原子制造技术获得的新型原子级材料,其结构和成核生长在材料科学、摩擦学、生物学、大气科学和行星科学等众多领域具有至关重要的作用.虽然二维冰的结构性质已被广泛研究,但对其电学和光学性质知之甚少.本文通过密度泛函理论和线性响应理论计算了二维冰相I在零温时的主要电学、光学、介电性质和红外光谱.其次,利用从头算分子动力学方法模拟得到了二维冰相I在有限温度下的声子振动态密度.本文的结果揭示了原子级二维冰相I的电子结构,同时展示了其独特的光吸收机理,有助于二维冰相I的进一步实验表征和原子级操控.由于表面上的二维冰可以促进或抑制三维冰的形成,这对于设计和研发防结冰材料具有潜在的应用价值.此外,二维冰本身也可以作为一种特殊的二维材料,为高温超导电性、深紫外探测、冷冻电镜成像等研究提供全新的标准材料.

Two-dimensional ice is a new type of atomic-scale material obtained by typical atomic manufacturing techniques.Its structure and nucleation growth play an essential role in many fields such as material science,tribology,biology,atmospheric science and planetary science.Although the structural properties of two-dimensional ice have been investigated extensively,little is known about its electronic and optical properties.In this paper,the main electronic,optical,dielectric properties and infrared spectra of two-dimensional ice Ⅰ at zero temperature are calculated by density functional theory and linear response theory.The study reveals that the two-dimensional ice Ⅰ is an indirect band gap and its optical properties show anisotropic lattice.And the absorption energy range for the two-dimensional ice Ⅰ is in the ultraviolet region of the spectrum(>3.2 eV)and the visible region of the spectrum(between 2 and 3.2 eV),respectively.Secondly,the radial distribution function and the vibrational density of states of the two-dimensional ice Ⅰ at a finite temperature are simulated by ab initio molecular dynamics method.For the structure of the two-dimensional ice I,whether SCAN or PBE functional,after considering the vdW effect,there is almost no effect on the atomic distance,while by comparison,the SCAN functional and the PBE functional are quite different.Therefore,it can be seen that the main reason for affecting the distance between atoms in the structure is due to the consideration of the strong confinement effect of SCAN.In terms of the vibration characteristics of two-dimensional ice Ⅰ,comparing with PBE and vdW-DF-ob86,the first two peaks of the IR spectrum of SCAN+rVV10 functional show blue shift,and the two peaks in the high frequency region present the red shift.Therefore,considering the strong confinement effect of SCAN,the intermolecular tensile vibration of two-dimensional ice Ⅰ becomes stronger,while the intramolecular H-O-H bending vibration and O-H bond tensile vibration become weaker.The effect of van der Waals action on vibration properties is not obvious.Furthermore,we investigate the temperature effects on the vibration spectra of two-dimensional ice Ⅰ.It is found that with the increase of temperature,the intermolecular librational mode weakens at a low frequency,the intramolecular bending and stretching bands gradually broaden,and the intramolecular O-H stretching peak presents the blue-shifts with temperature rising.The results of this paper reveal the electronic structure of atomic-scale two-dimensional ice Ⅰ,and demonstrate its unique optical absorption mechanism,which is helpful in further experimentally characterizing and manipulating the two-dimensional ice on an atomic scale.Since the two-dimensional ice on the surface can promote or inhibit the formation of three-dimensional ice,it has potential applications in designing and developing the anti-icing materials.In addition,two-dimensional ice itself can also be used as a unique two-dimensional material,providing a brand-new standard material for high-temperature superconductivity,deep-ultraviolet detection,cryo-electron microscopy imaging.