Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, Møller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from http://www.daltonprogram.org for a number of UNIX platforms.

Satellite products of chemical species have a big potential to improve the accuracy of chemical transport models via data assimilation. This report deals with the development of the basic building blocks for a future variational data assimilation system constructed around the Unified EMEP model. The development of a 1D- VAR system for tropospheric NO 2 column from GOME provided the basic testing and development ground in which to start such development. The statistical comparison between co-located model results and GOME tropo- spheric NO 2 column show spatial correlations in agreement with what is observed for ground NO 2 concentration. This preliminary results indicate the potential us- age of this satellite product on the future 3D-VAR data assimilation system. This reinforces the long term development plans for the forecast system and the assim- ilation of satellite products. Nevertheless, the spatial and temporal structure of the bias needs further investigation in order to develop a bias correction module, before it is used in an operational data assimilation system.

An operational assimilation system incorporating significant wave height observations in high resolution numerical wave models is studied and evaluated. In particular, altimeter satellite data provided by the European Space Agency (ESA-ENVISAT) are assimilated in the wave model WAM which operates in two different wave climate areas: the Mediterranean Sea and the Indian Ocean. The first is a wind-sea dominated area while in the second, swell is the principal part of the sea state, a fact that seriously affects the performance of the assimilation scheme. A detailed study of the different impact is presented and the resulting forecasts are evaluated against available buoy and satellite observations. The corresponding results show a considerable improvement in wave forecasting for the Indian Ocean while in the Mediterranean Sea the assimilation impact is restricted to isolated areas.

Activation of methane by oxidative addition and sigma-bond metathesis has been investigated for (N-N)M(CH3) (M = Pd+, Pt+, Rh+, Ir+, Rh, Ir; N-N = (HN=CH-CH=NH) using different density functional approaches. The pathway of oxidative addition is in general favored, the exceptions being Pd+ and Rh+. Oxidative addition is clearly more favorable for the third-row metal complexes than those of the second row. The third-row metal complexes also tend to have a lower activation barrier for sigma-bond metathesis than those of the second row. In each case, the oxidative addition is preceded by formation of a sigma complex. The bonding energies of these complexes are significantly stronger for the cationic systems. (C) 2003 Wiley Periodicals, Inc.

Different density functional theory (DFT) functionals have been evaluated by studying geometries and bond strengths of YbH, YbF, EuF, GdF, and NdF and compared with accurate CCSD(T) results and, when available, experiment. The agreement between the CCSD(T) results and experiment, when available, is good. The agreement is also good between bond strengths calculated at the DFT level using relativistic effective core potentials and the CCSD(T) results. However, the all-electron ADF calculations systematically overestimate binding energies. The geometries obtained by both the all-electron and the effective-core-potential-based DFT calculations are generally in good agreement with the CCSD(T) results.

The elementary steps of a recently reported methane activation reaction involving a platinum complex with a bidentate nitrogen ligand have been investigated using quantum chemical methods based on density functional theory. Our findings support a reaction mechanism involving formation of a sigma-complex followed by oxidative addition.