Vesa Hänninen

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We employ ab initio methods to find stable geometries and to calculate potential energy surfaces and vibrational wavenumbers for sulfuric acid monohydrate. Geometry optimizations are carried out with the explicitly correlated coupled-cluster approach that includes single, double, and perturbative triple excitations (CCSD(T)-F12a) with a valence double-ζ(More)
We have carried out a detailed investigation of the acceptor tunneling in the water dimer. This motion is responsible for the largest splitting of vibrational states in the dimer, the so-called acceptor splitting. Our results confirm that this splitting is due to a coupled 2-fold motion: The internal rotation of the donor with respect to the O-O axis, and(More)
Dispersion interactions in small clusters of group XII (Zn, Cd, Hg) metal atoms are studied at the CCSD(T) level with triple-ζ basis sets. A pair potential model together with a least-squares fit to the interaction potential energy surface is used to calculate interatomic dispersion coefficients, which are found to be in good agreement with atomistic(More)
This work contains studies in theoretical and computational spectroscopy of methanol, partially deuterated silane, and bismutine. Vibrational spectra of methanol have been simulated in the fundamental, first C-H stretching overtone, and O-H stretching overtone regions using both normal and local mode models. A vibration-torsion local mode model based on(More)
We employ ab initio calculations of van der Waals complexes to study the potential energy parameters (C(6) coefficients) of van der Waals interactions for modeling of the adsorption of silver clusters on the graphite surface. Electronic structure calculations of the (Ag(2))(2), Ag(2)-H(2), and Ag(2)-C(6)H(6) complexes are performed using a coupled-cluster(More)
We use state-of-the-art electronic structure calculation methods and large basis sets to obtain reliable values for the thermodynamic properties of sulfuric acid monohydrate and study the effects of vibrational anharmonicity on these properties. We distinguish between two forms of vibrational anharmonicity: local anharmonicity, which refers to the(More)
The effects of shore hardness, static load, frequency, and intensity of vibration on the amplitude and dynamic force effects of vibration were studied in conditions corresponding to those occurring in vibrotactile sensitivity measurements. The measurements were performed on three silicon plates of known shore hardness. The results indicated that the effect(More)
The O-H stretching vibrational overtone spectrum of the water dimer has been calculated with the dimer modeled as two individually vibrating monomer units. Vibrational term values and absorption intensities have been obtained variationally with a computed dipole moment surface and an internal coordinate Hamiltonian, which consists of exact kinetic energy(More)
We have developed a model to calculate accurately the intensity of the hydrogen bonded XH-stretching vibrational transition in hydrogen bonded complexes. In the Local Mode Perturbation Theory (LMPT) model, the unperturbed system is described by a local mode (LM) model, which is perturbed by the intermolecular modes of the hydrogen bonded system that couple(More)
We present a novel formulation for the intermolecular interaction tensor, which is used to describe the long-range electrostatic, induction, and dispersion interactions. Our formulation is based on concepts drawn from combinatorial analysis and Clifford calculus and enables us to present the interaction tensor in a form that is simple to use and suitable(More)