Combined gas electron diffraction/mass spectrometric study of beryllium diiodide assisted by quantum chemical calculations: structure and thermodynamics of beryllium dihalides

摘要

Molecular structure of beryllium diiodide, BeI2, was studied by combined gas-phase electron diffraction/mass spectrometry experiment at two temperatures, 501(5) and 722(10) K, and by theoretical calculations. Equilibrium structure of the monomer was found to be linear; thermal-averaged bond distance r (g)(Be-I) = 2.163(6) and 2.172(7) was determined for the low- and high-temperature experiment, respectively. Quantum chemical approaches DFT-B3LYP, MP2 and CCSD(T) were applied to calculate the geometric and vibration parameters of monomeric and dimeric Be2X4 (X = F, Cl, Br, I) molecules. Enthalpies of the dimerization processes 2BeX(2)(g) = Be2X4(g) were estimated on the base of quantum chemical results with the basis set superposition error (BSSE) taken into account and compared with the experimental thermodynamic values.