| Using the aug-cc-pVDZ basis set supplemented with bond functions (BF), the existences of the systems (FH)2{e}(HF)2 have been studied. It was found to have equilibrium geometry with all frequencies real at the second-order M?ller-Plesset perturbation (MP2/aug-cc-pvdz+BF) level. The calculated vertical electron detachment energy (VDE) is 1.065 eV for (FH)2{e}(HF)2 at the coupled cluster level of theory with single, double, and noniterative triple excitations (CCSD(T)). The result calculated indicated that the stabilities of the system own to forming the monoelectron dihydrogen bond H···e···H, which comes not only from the static Coulomb interaction but also from the dispersion interaction between the loosely bound (excess) electron and the neutral molecular (cluster's) hosts. The characteristics of the monoelectron dihydrogen bond H···e···H of the system have been revealed. The H···e···H bond length is 2.359? for (FH)2{e}(HF)2. Some vibrational modes that display the presence of the bond H···e···H have been found and a novel secondary interaction, H-bond-excess electron attracting has been discussed. Using aug-cc-pVDZ basis sets supplemented with diffused bond functions, the (H2O)4- isomer of the water tetramer anion in Ci-symmetry was optimized at the MP2 level. The excess electron was enveloped directly by the four hydrogen atoms of two inside water molecules, forming an interior structure. This study shows four hydrogen atoms of two outside water molecules also have important interaction with the trapped electron. We described the interactions between individual water molecule (including both inside and outside) and the trapped electron. The influence of the trapped electron on the surrounded second layer molecules was also put forward. Using the aug-cc-pVDZ basis set supplemented with diffuse bond functions (BF), The evolution of the monoelectron dihydrogen bond H···e···H in the symmetric (n = m = 2-5) and asymmetric (n, m: 3, 1; 3, 2; 4, 2; 4, 3) cluster anions (FH)n{e}(HF)m have been studied. When n = m = 3, 4, 5 and n, m: 3, 2 the H···e···H bond evolves into the FH-e-HF monoelectron bimolecular bond. While in some asymmetric cluster anions (n, m: 4, 2; 4, 3) the FH-e-HF bond changes to H-e-HF bond, and some bond rearrangements happen in the larger subunit (HF)4 at the same time. This evolution shows a size effect of the subunits on the structure and the bond for the molecular cluster anions.Using the 6-311++G(3df,2p) basis set, the clusters BeB4X4 (X=H,F.Cl), HBB4H4 and BB4H4+ which all have a square pyramidal shape were got at the second-order M?ller-Plesset perturbation (MP2) level with all frequencies real. The vertexes of these square pyramidal clusters are Be, BH and B separately. They all act as a two electron donor for B4X4, and the B4X4 act as a bowl to accommodate the pair of electrons. The interaction energies between the vertexes and the B4X4 bowls were calculated at the CCSD(T) level. The interactions between bowls with different terminal atoms and transferred electrons were discussed. The character of the B4 ring is affected deeply with the terminal atoms. For HBB4H4 and BB4H4+, they are four and six electrons short of the Wade magic electron count, but they all have their strong bonding here.
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