A comprehensive theoretical study of positron binding and annihilation properties of hydrogen bonded binary molecular clusters
A comprehensive theoretical study of positron binding and annihilation properties of hydrogen bonded binary molecular clusters
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氢键二元分子簇正电子结合和湮没特性的综合理论研究
DOI：
10.1039/d2cp03813g
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发表时间：
2022
影响因子：
3.3
通讯作者：
Masanori Tachikawa
中科院分区：
文献类型：
--
作者：
Daisuke Yoshida;Yukiumi Kita;Tomomi Shimazaki;Masanori Tachikawa
我们利用第一性原理计算研究了含有小无机分子（例如水、氟化氢、氨、硫化氢、氯化氢和磷化氢）的氢键二元分子簇的正电子结合和湮灭。虽然这些物种的单分子系统大多不表现出或表现出非常小的正电子结合能（正电子亲和力），但我们发现它们所有的氢键簇都具有更大的正正电子亲和力。通过分子间氢键的形成而增强的永久偶极矩充当结合给定质子供体的正电子的主要参数，而其不足以再现正电子亲和力对质子供体取代的依赖性。通过对团簇固有特性的多元回归分析，我们找到了一个合理的模型，其中包含额外的有效参数，特别是不含氢键的氢原子的数量。通过对单粒子和正负电子碰撞概率的密度分析，我们发现这些有效参数与氢键和正电子结合引起的电子结构变化有关，由于质子屏蔽效应，这些变化对于提高正负电子接触密度具有重要作用。
We studied the positron binding and annihilation of hydrogen bonded binary molecular clusters containing small inorganic molecules such as water, hydrogen fluoride, ammonia, hydrogen sulfide, hydrogen chloride, and phosphine, using first-principles calculation. While unimolecular systems of these species mostly exhibit no or very small positron binding energies (positron affinities), we found that all of their hydrogen bonding clusters have greater positive positron affinities. The permanent dipole moment enhanced by the formation of the intermolecular hydrogen bond acts as a dominant parameter to bind a positron for a given proton donor, whereas it is insufficient for reproducing the dependence of the positron affinity on substitutions of the proton donor. By multiple regression analyses with inherent properties of the clusters, we found a reasonable model with additional effective parameters represented by, particularly, the number of hydrogen atoms free from the hydrogen bond. By density analyses for the single-particle and electron–positron collision probabilities, we revealed that these effective parameters are associated with the electronic structure changes induced by the hydrogen bond and positron binding, which have important roles to enhance the electron–positron contact densities due to the proton-screening effect.