Laboratory of Theoretical Chemistry, Namur Institute of Structured Matter (NISM), University of Namur, Rue de Bruxelles, 61, B-5000, Namur, Belgium.
ChemistryOpen. 2023 Jan;12(1):e202200045. doi: 10.1002/open.202200045. Epub 2022 Aug 11.
The Sequential Quantum Mechanics/Molecular Mechanics scheme has been enacted to perform a systematic investigation of the polarizability (α) and first hyperpolarizability (β) responses at the water-vacuum interface. After performing classical molecular dynamics simulations to provide snapshots of the structures, quantum chemistry calculations of the linear and nonlinear optical responses have been performed for clusters of five water molecules at the time-dependent DFT level in combination with different embedding schemes, ranging from point charges to polarizable point charges, with and without local field effects. When going from the bulk to the interface, the main observations of these calculations encompass i) a modest increase of the average polarizability but an increase by about a factor of two of its anisotropy, ii) an increase by about 20 % of the β response, accompanied by a small increase of its depolarization ratio, and iii) a net increase of the component of the β tensor normal to the interface (β ) as well as of β . Globally, the interfacial effects on β are localized at the first molecular layer while they are observed up to the fourth molecular layer on α.
已采用序贯量子力学/分子力学方案，以系统地研究真空-水界面处的极化率（α）和一阶超极化率（β）响应。在进行经典分子动力学模拟以提供结构快照之后，已针对五个水分子的簇在含时密度泛函理论水平上进行了线性和非线性光学响应的量子化学计算，结合了不同的嵌入方案，范围从点电荷到极化点电荷，有和没有局部场效应。从本体到界面时，这些计算的主要观察结果包括：i）平均极化率略有增加，但各向异性增加了约两倍；ii）β响应增加约 20％，同时其去极化比略有增加；iii）与界面垂直的β张量的分量（β⊥）以及β都有净增加。总体而言，β的界面效应局限于第一层分子，而在α上，这种效应可以观察到第四层分子。
