In this work a reliable full nine-dimensional potential energy surface for studying the dynamics of H(5)(+) is constructed, which is completely symmetric under any permutation of the nuclei. For this purpose, we develop a triatoms-in-molecules method as an extension of the more common diatoms-in-molecules one, which allows a very accurate description of the asymptotic regions by including correctly the charge-induced dipole and quadrupole interactions. Moreover, this treatment provides a semiquantitative description of all the topological features of the global potential compared with coupled cluster results. In particular, the hop of the proton between two H(2) fragments produces a double well in the potential. This resonant structure involving the five atoms produces a stabilization, lowering the barrier, and the triatoms-in-molecules yields to a barrier significantly higher than the ab initio results. Therefore, to improve the triatomics-in-molecules potential surface, two five-body terms are added, which are fitted to more than 110,000 coupled-cluster ab initio points. The global potential energy surface thus obtained in this work has an overall root mean square error of 0.079 kcal/mol for energies below 27 kcal/mol above the global well. The features of the potential are described and compared with previous available surfaces.

Ab initio intermolecular potential energy surface, bound states, and microwave spectra for the van der Waals complex Ne-HCCCN

A new embedding method to include local correlation in large systems is proposed. In this method the density of the whole system, calculated via density functional theory approaches, is partitioned in two pieces, one corresponding to the subsystem of interest and the rest to the environment. In the second step, an embedding potential is obtained iteratively using as a driving force the self-repulsion due to the density difference, in a similar form as proposed by Zhao et al. [Phys. Rev. A 50, 2138 (1994)], to obtain the "exact" exchange-correlation functional. Such potential is added to the Fock equation to build the localized molecular orbitals which are further used to include the local electronic correlation in the subsystem of interest. This method is an alternative to the previous DFT-based embedding methods first proposed by Wesolowski and Washell [J. Phys. Chem. 97, 8050 (1993)] and after enhanced by Govind et al. [J. Chem. Phys. 110, 7677 (1999)] and adapted to metal extended systems, which use density functionals to describe the kinetic energy contribution to the embedding potential, whose precise form has been largely treated in the literature and its crucial role is discussed here. The method is applied to hydrogen chains and its van der Waals interaction with H(2). The results obtained are in very good agreement with exact calculations performed on the whole system, which demonstrates that the method proposed is a very promising route to introduce correlation in large systems.

An approximate quantal treatment to obtain the energy levels of tetraatomic XI2Y van der Waals clusters (X,Y=He,Ne) A variational treatment is presented to study bound and quasibound states of XI'" BC'" X z van der Waals clusters, where XI and X 2 are rare gas atoms and BC is a conventional diatomic molecule. The Hamiltonian operator, including all the degrees of freedom, is expressed in terms of the B-C relative vector and bond coordinates which describe the position of each rare gas atom with respect to the BC center of mass. In a body-fixed reference system, with the Z axis parallel to the diatomic axis, all the matrix elements of the Hamiltonian are evaluated in a basis set of functions which takes into account the symmetries of the system. Numerical applications to the He2'''C12 and Ne2"'12 complexes are presented and discussed.

Use of correlated potential harmonic basis functions for the description of the 4He trimer and small clusters J. Chem. Phys. 134, 164106 (2011); 10.1063/1.3583365Bound-state energies in argon trimers via a variational expansion: The effects from many-body corrections Helium trimer bound states are calculated by means of a variational method described in terms of atom pair coordinates and distributed Gaussian basis functions for zero total angular momentum. To show the feasibility of this method, we also apply it to the calculation of the first vibrational levels of the Ar 3 and Ne 3 clusters. Special emphasis is made on the study of the possible Efimov behavior of the first excited state found in the 4 He 3 trimer. Geometrical configurations of the ground and first excited states of these rare gas trimers have been exhaustively studied owing to the proper symmetry of the coordinates chosen.

Articles you may be interested in A full-dimensional quantum approach to the vibrational predissociation of tetra-atomic complexes based on the partially-separable time-dependent self-consistent-field approximation Oneatom cage effect in collinear I2(B)-Ar complexes: A timedependent wave packet study Validity of a hybrid quantum/classical approach in photodissociation/recombination of I2 in rare gas matrices A three-dimensional time-dependent self-consistent-field TDSCF approach is proposed to study the vibrational predissociation of the I 2 (B)-Ne van der Waals vdW complex. Jacobian coordinates are used within the assumption of zero-total angular momentum. In the method the total wave function is factorized such that the bending mode of the system is explicitly separated, while the coupling between the remaining two degrees of freedom is treated exactly. The decay dynamics of several resonances corresponding to different initial vibrational states of I 2 is investigated through long-time wave packet propagations. Calculated resonance lifetimes are compared to experimental data and found to be in quantitative agreement with them. The results show that predissociation of the complex is mainly governed by the coupling between the I 2 and the vdW stretching vibrations, whereas the bending mode has a rather weak effect on the dynamics. The good quality of the TDSCF description of this long-time dynamical process is due to the adaptation of the decoupling approximations applied in the method to the physical situation of the system. The validity of the approach is discussed in the light of the results.

No abstract

Coronene-doped helium clusters have been studied by means of classical and quantum mechanical (QM) methods using a recently developed He-C24H12 global potential based on the use of optimized atom-bond improved Lennard-Jones functions. Equilibrium energies and geometries at global and local minima for systems with up to 69 He atoms were calculated by means of an evolutive algorithm and a basin-hopping approach and compared with results from path integral Monte Carlo (PIMC) calculations at 2 K. A detailed analysis performed for the smallest sizes shows that the precise localization of the He atoms forming the first solvation layer over the molecular substrate is affected by differences between relative potential minima. The comparison of the PIMC results with the predictions from the classical approaches and with diffusion Monte Carlo results allows to examine the importance of both the QM and thermal effects.