InOH: A quantum chemical study

The structure and energetics of the InOH molecule were thoroughly studied u sing higher level ab initio and density functional theories for the first t ime. 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 agree ment with recent experimentally determined values. The use of triple-zeta p lus double polarization with diffusion function basis set was required to r eproduce the experimental values. The bent structure of the InOH molecule i s energetically more stable than the linear structure. Because the energy d ifference 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 molec ule might best be characterized as quasilinear. This finding is consistent with the potential energy curve being flat when the relative energy is plot ted as a function of theta. The linear structure has one imaginary frequenc y 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, r espectively, are greater than that for many alkali and alkaline-earth hydro xides. The predicted HInO isomer is less stable than the InOH molecule by 5 9.2 kcal/mol, at the QCISD level.