Quantum states of the endohedral fullerene Li+@C60 surrounded by anions: energy decomposition analysis of nuclear wave functions
Quantum states of the endohedral fullerene Li+@C60 surrounded by anions: energy decomposition analysis of nuclear wave functions
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DOI：
10.1039/d1cp00056j
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发表时间：
2021-03-18
影响因子：
3.3
通讯作者：
Nakao，Yoshihide
中科院分区：
文献类型：
--
作者：
Ando，Hideo;Nakao，Yoshihide
锂是最轻的金属元素。迄今为止，人们对它在纳米多孔结构中的量子化核运动知之甚少。内嵌富勒烯Li+@C60是研究这种量子化运动的理想多孔体系。最近的研究表明，C60笼外部周围的阴离子和轻微的笼变形可以改变笼内部的势场，从而改变Li+的核波函数。电子态，特别是C60笼的柔性π电子云，如何与Li+波函数的定域化（去定域化）相关联还有待澄清。以[Li+@C60] PF 6 −晶体为研究对象，建立了考虑PF 6 −配位和笼形畸变的局域结构模型。我们开发的模型函数，适合后Hartree-Fock势能面的Li+运动及其分解的组件，四个相互作用能量表面。这种分解澄清了壳状吸附剂势的起源和其中的势威尔斯阱。傅立叶网格哈密顿方法使我们能够获得低能量Li+波函数。基态是近两倍简并的，其波函数主要位于两个C6环之下，靠近X射线晶体结构中Li+的无序位。通过扩展能量分解分析内的钳位核近似，将核波函数的离域，我们证明了基态是稳定的极化，色散和静电相互作用。除了Li+在经典静电场中移动的常见图像之外，我们的方法将加深对各种分子间相互作用限制在可极化多孔结构中的灵活Li+波函数的理解。
Lithium is the lightest metal element. To date, little is known about its quantized nuclear motion in nanoscale porous structures. Endohedral fullerene Li+@C60 is an ideal porous system for studying such a quantized motion. Recent studies suggest that the anions surrounding the C60 cage exterior and a slight cage distortion can alter the potential field in the cage interior and thus the nuclear wave function of Li+. It has yet to be clarified how the electronic state, particularly the flexible π electron cloud of the C60 cage, is associated with (de)localization of the Li+ wave function. Focusing on the [Li+@C60]PF6− crystal, we constructed a local structure model considering the PF6− coordination and the cage distortion. We developed model functions that fit the post-Hartree–Fock potential energy surface for the Li+ motion and its decomposed components, four interaction energy surfaces. The decomposition clarified the origins of the shell-like adsorbent potential and the potential wells therein. The Fourier grid Hamiltonian method allowed us to obtain low-energy Li+ wave functions. The ground state is nearly two-fold degenerate, and its wave functions are mostly localized underneath two C6 rings, near the disordered sites of Li+ in the X-ray crystal structure. By extending the energy decomposition analysis within the clamped-nuclei approximation to incorporate the delocalization of nuclear wave functions, we demonstrated that the ground state is stabilized by the polarization, dispersion, and electrostatic interactions. Beyond the common picture of Li+ moving in a classical electrostatic field, our approach will deepen the understanding of the flexible Li+ wave function confined in a polarizable porous structure by various intermolecular interactions.