| 1. |
- Aidas, Kestutis, et al.
(författare)
-
The Dalton quantum chemistry program system
- 2014
-
Ingår i: Wiley Interdisciplinary Reviews. Computational Molecular Science. - : Wiley. - 1759-0876. ; 4:3, s. 269-284
-
Tidskriftsartikel (refereegranskat)abstract
- 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, MOller-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 for a number of UNIX platforms.
|
|
| 2. |
|
|
| 3. |
- Gomes, Andre Severo Pereira, et al.
(författare)
-
Applied Computational Actinide Chemistry
- 2015
-
Ingår i: Computational Methods in Lanthanide and Actinide Chemistry. - Chichester : John Wiley & Sons. - 9781118688304 - 9781118688311 ; , s. 269-298
-
Bokkapitel (refereegranskat)abstract
- The theoretical modeling of lanthanide and actinide complexes in condensed media is challenging for theoretical chemistry, due in part to the intrinsic general challenge of devising a reliable model of the species in such environments and the necessity of ‘chemical’ accuracy. This chapter discusses the requirements, challenges, and pitfalls associated with attempting to theoretically model molecular properties for such systems that can be directly compared to experimental data, such as valence excitation spectra, core-excitation spectra, thermodynamics of chemical reactions, and redox properties. Spin-orbit effects are in general important to account for in excited-states calculations and in chemical reactions involving trans-uranium actinides and in many cases also uranium complexes. The most rigorous framework to include spin-orbit interaction is to treat it a priori in a four- or two-component relativistic framework. The Ultraviolet–visible (UV-Vis) spectroscopy of lanthanide and actinide elements directly reflects the electronic structure of the species involved.
|
|
| 4. |
- Karlström, Gunnar, et al.
(författare)
-
MOLCAS : a program package for computational chemistry
- 2003
-
Ingår i: Computational materials science. - 0927-0256 .- 1879-0801. ; 28:2, s. 222-239
-
Tidskriftsartikel (refereegranskat)abstract
- The program system MOLCAS is a package for calculations of electronic and structural properties of molecular systems in gas, liquid, or solid phase. It contains a number of modern quantum chemical methods for studies of the electronic structure in ground and excited electronic states. A macromolecular environment can be modeled by a combination of quantum chemistry and molecular mechanics. It is further possible to describe a crystalline material using model potentials. Solvent effects can be treated using continuum models or by combining quantum chemical calculations with molecular dynamics or Monte-Carlo simulations. MOLCAS is especially adapted to treat systems with a complex electronic structure, where the simplest quantum chemical models do not work. These features together with the inclusion of relativistic effects makes it possible to treat with good accuracy systems including atoms from the entire periodic system. MOLCAS has effective methods for geometry optimization of equilibria, transition states, conical intersections, etc. This facilitates studies of excited state energy surfaces, spectroscopy, and photochemical processes.
|
|
| 5. |
|
|
| 6. |
- Rubio Pons, Oscar, et al.
(författare)
-
CASSCF calculations of triplet-state properties : Applications to benzene derivatives
- 2003
-
Ingår i: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 101:13, s. 2103-2114
-
Tidskriftsartikel (refereegranskat)abstract
- We illustrate the capability of the complete active space self-consistent field method by Roos and co-workers for calculations of triplet state properties. We report phosphorescence lifetimes, zero-field splitting parameters, and nuclear quadrupole coupling constants for the lowest triplet state of a variety of benzene derivatives.
|
|
| 7. |
- Wåhlin, Pernilla, 1968-, et al.
(författare)
-
On the combined use of discrete solvent models and continuum descriptions of solvent effects in ligand exchange reactions : a case study of the uranyl(VI) aquo ion
- 2009
-
Ingår i: Theoretical Chemistry accounts. - : Springer Science and Business Media LLC. - 1432-881X .- 1432-2234. ; 124:5-6, s. 377-384
-
Tidskriftsartikel (refereegranskat)abstract
- Modeling of the solvent is important when using quantum chemical methods for the assignment of mechanisms from experimental studies of the exchange of water between metal aquo ions and the bulk solvent. In the present study, we have investigated if and how the mechanisms for water exchange in the UO2(OH2)(5)(2+)-H2O system is affected by the choice of chemical models for the second coordination sphere and physical models for describing the cavity in conductor-like polarizable continuum (CPCM) models. In the first case, we have compared models with one and five waters in the second coordination sphere. For both models, we have compared cavities in which each atom is assigned one spherical cavity and one in which the water molecules are described by a single spherical cavity (the United Atom model). There are significant differences in the relative energy of dissociative and associative intermediates; however, they are not large enough to affect the conclusion that the water exchange proceeds through an associative/interchange mechanism.
|
|
