Vibrational analysis and ionization potentials of XCH3 (X=Be,Mg,Ca) calculated by hybrid density functional theory and high order ab initio methods

The amount of attention dedicated to the theoretical and experimental investigation of small cationic organometallic systems in the literature is very limited. In this Letter we use the B3LYP method with a variety of basis sets as well as the very advanced CBS-Q, CBS-QB3, G1, G2MP2, G2, G3, and G3B3 ab initio methods in order to analyze the vibrational spectra as well as ionization potentials of BeCH₃,MgCH₃ and CaCH₃. The need for further addition of experimental data to the archives for these systems is discussed, as well as recommendations for which theoretical methods are optimum for a particular result.