InOH: A quantum chemical study

The structure and energetics of the InOH molecule were thoroughly studied using higher level ab initio and density functional theories for the first time. The bond angle, theta(InOH), and harmonic vibrational frequency, nu(2) (bending), calculated using a 6-311++G(2d,2p) basis set were in good agreement with recent experimentally determined values. The use of triple-zeta plus double polarization with diffusion function basis set was required to reproduce the experimental values. The bent structure of the InOH molecule is energetically more stable than the linear structure. Because the energy difference between the two structures is very small, 0.22 and 0.20 kcal/mol using the QCISD(T) and CCSD(T) levels, respectively, the shape of the molecule might best be characterized as quasilinear. This finding is consistent with the potential energy curve being flat when the relative energy is plotted as a function of theta. The linear structure has one imaginary frequency corresponding to its bending mode. The bond dissociation energies, D-o(In-OH), of 4.33 and 4.32 eV obtained using the QCISD(T) and CCSD(T) levels, respectively, are greater than that for many alkali and alkaline-earth hydroxides. The predicted HInO isomer is less stable than the InOH molecule by 59.2 kcal/mol, at the QCISD level.