β-PTCDA的电子结构和光学性质的第一性原理计算（英文）

Electronic Structures and Optical Properties of β-PTCDA Based on the First-Principles Investigation

基于密度泛函理论,采用第一性原理赝势平面波方法研究了β-PTCDA分子晶体的能带结构、分波态密度和光学性质,通过分析不同种类原子的不同电子态在不同电子能级中的贡献,获得β-PTCDA分子晶体的光频介电常数、光吸收系数、折射率和能量损失函数等随光频的变化规律.结果表明：β-PTCDA作为一种直接带隙的窄带隙有机半导体,对费米能级贡献较大的电子轨道为苝核的C 2p以及O 2p电子态,即价带顶;对导带底贡献较大的为C 2p及O 2p电子态,包括酸酐C原子;其在光子能量为2~10eV的区域具有强的光吸收特性,以及明显的双轴各向异性;在介电函数实部ε1（ω）〈0的光频区域,β-PTCDA分子晶体具有各向异性电导率,且与能量损失函数相一致.

Electronic band structure,Partial Density of States（PDOS）and optical properties ofβ-phase3,4,9,10-perylenetetracarboxylic dianhydride（β-PTCDA） molecular crystal were systematically investigated by first-principles calculations based on Density Functional Theory（DFT）.The contribution of different type of atoms electronic states to different electronic levels was analyzed,and the frequency dependent optical functions such as the dielectric function,absorption coefficient,refractive index and energy loss function ofβ-PTCDA molecular crystal that changed with optical frequency were analyzed and obtained.The results showed thatβ-PTCDA is a direct narrow band gap semiconductor,and the electron orbit making larger contribution to the Fermi level is the O 2p electronic state and C 2p electronic state that come from the perylene core,which are also the top of valence band;what makes larger contribution to the bottom of the conduction band is also the C 2p and O 2p electronic states,including anhydride C atoms;in the photon energy range of 2to 10 eV,the strong light absorption and obvious biaxial anisotropy can be observed.In the optical frequency range with the real part of dielectric functionε1（ω）0,β-PTCDA molecular crystal has an anisotropic conductivity,which is consistent with the energy loss function.