High-level electronic structure calculations are performed to elucidate the Be–Be chemical bond in the (NH₃)_nBe–Be(NH₃)_n species for n = 0–4. We show that the Be₂ bond is explained as a resonance between two Lewis structures, where one beryllium atom donates an electron pair to the second one, and vice versa. The presence of ammonia ligands enhances the stability of this bond considerably. The ∼2.5 kcal/mol binding energy of Be₂ becomes ∼30 kcal/mol for [Be(NH₃)_1–3]₂ because of their more polarizable electron pairs. The larger Be(NH₃)₄ complex has been classified as a solvated electron precursor in the past and has an electron pair in the periphery of a Be(NH₃)₄²⁺ core occupying a diffuse s-type orbital. The analogy of Be(NH₃)₄ to Be reflects into the electronic structure of their dimers. The two systems have identical bonding patterns and low-lying electronic states. The ground state binding energy of [Be(NH₃)₄]₂ is 3 times larger than Be₂, and its excitation energies are considerably lower by a factor of 3. We also studied the dimers of the cationic Be(NH₃)_n⁺ species, and we found that the Coulombic repulsion is counterbalanced by the formation of a single covalent bond in the cases of n = 1, 2 forming stable dicationic [(NH₃)_nBe–Be(NH₃)_n]²⁺ systems, unlike Be₂²⁺. We believe that our numerical results will allow the identification and characterization of these exotic species and their solid state (beryllium liquid metals) analogues in future experiments.

中文翻译：

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行动中的“ Be-Be键”：铍-氨络合物的经验教训[Be（NH ₃）_0–4 ] ₂ ^0,2+

进行高级电子结构计算以阐明n = 0–4的（NH ₃）_n Be–Be（NH ₃）_n物种中的Be–Be化学键。我们表明，Be ₂键被解释为两个Lewis结构之间的共振，其中一个铍原子将电子对提供给第二个，反之亦然。氨配体的存在大大提高了该键的稳定性。对于[Be（NH ₃）_1-3 ] ₂来说，Be _2的约2.5 kcal / mol的结合能变为约30 kcal / mol，因为它们具有更多可极化的电子对。较大的Be（NH ₃）₄过去，该配合物已被分类为溶剂化电子前体，并且在Be（NH ₃）₄ ²⁺核的外围具有电子对，该电子对占据了扩散的S型轨道。Be（NH ₃）₄与Be的类比反映在其二聚体的电子结构中。这两个系统具有相同的键合模式和低电子状态。[BE（NH的基态结合能₃）₄ ] ₂大于更大3次₂，和它的激发能量通过的3倍的显着地降低我们还研究的二聚体阳离子成为（NH ₃）_ñ ⁺物种，我们发现在n = 1、2形成稳定的dicicic [（NH ₃）_n Be–Be（NH ₃）_n ] ²⁺系统时，通过形成一个共价键可以抵消库仑排斥力，不像Be ₂ ²⁺。我们相信，我们的数值结果将有助于在未来的实验中鉴定和表征这些外来物种及其固态（铍液态金属）类似物。