Chen Bole, Gutsev Gennady L, Sun Weiguo, Kuang Xiaoyu, Lu Cheng, Gutsev Lavrenty G, Aldoshin Sergey M, Ramachandran Bala R
Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China.
Phys Chem Chem Phys. 2021 Jan 28;23(3):2166-2178. doi: 10.1039/d0cp05427e.
The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster were studied using density functional theory with the generalized gradient approximation and a basis set of triple-zeta quality. It was found that the coalescence may proceed without an energy barrier and that the geometrical structures of the resulting clusters depend strongly on the mutual orientations of the initial moieties. The dissociation of N2 is energetically favorable on Fe16, and the nitrogen atoms share the same Fe atom in the lowest energy state of the Fe16N2 species. The attachment of two nitrogen atoms leads to a decrease in the total spin magnetic moment of the ground-state Fe16 host by 6 μB due to the peculiarities of chemical bonding in the magnetic clusters. In order to gain insight into the dependence of properties on charge and to estimate the bonding energies of both N atoms, we performed optimizations of Fe16N and the singly charged ions of both Fe16N2 and Fe16N. It was found that the electronic properties of the Fe16N2 cluster, such as electron affinity and ionization energy, do not appreciably depend on the attachment of nitrogen atoms but that the average binding energy per atom changes significantly. The lowering in total energy due to the attachment of two N atoms was found to be nearly independent of charge. The IR and Raman spectra were simulated for Fe16N2 and its ions, and it was found that the positions of the most intense peaks in the IR spectra strongly depend on charge and therefore present fingerprints of the charged states. The chemical bonding in the ground-state Fe16N20,±1 species was described in terms of the localized molecular orbitals.
利用广义梯度近似和三ζ质量基组的密度泛函理论研究了两个Fe8N的聚结以及Fe16N2团簇的结构。结果发现，聚结过程可能无能量势垒进行，且所得团簇的几何结构强烈依赖于初始部分的相互取向。N2在Fe16上的解离在能量上是有利的，并且在Fe16N2物种的最低能量状态下，氮原子共享同一个Fe原子。由于磁性团簇中化学键的特殊性，两个氮原子的附着导致基态Fe16主体的总自旋磁矩降低6 μB。为了深入了解性质对电荷的依赖性并估计两个N原子的结合能，我们对Fe16N以及Fe16N2和Fe16N的单电荷离子进行了优化。结果发现，Fe16N2团簇的电子性质，如电子亲和能和电离能，对氮原子的附着没有明显依赖性，但每个原子的平均结合能变化显著。发现由于两个N原子的附着导致的总能量降低几乎与电荷无关。对Fe16N2及其离子的红外和拉曼光谱进行了模拟，结果发现红外光谱中最强峰的位置强烈依赖于电荷，因此呈现出带电状态的指纹特征。基态Fe16N20,±1物种中的化学键用定域分子轨道进行了描述。
