Jan Kozicki

Potential energy surfaces of the low-lying electronic states of the Li + LiCs system

Abstract Ab initio quantum chemistry calculations are performed for the mixed alkali triatomic system. Global minima of the ground and first excited doublet states of the trimer are found and Born-Oppenheimer potential energy surfaces of the Li atom interacting with the LiCs molecule were calculated for these states. The lithium atom is placed at various distances and bond angles from the lithium-caesium dimer. Three-body nonadditive forces of the Li 2 Cs molecule in the global minimum are investigated. Dimer-atom interactions are found to be strongly attractive and may be important in the experiments, particularly involving cold alkali polar dimers.

Study of some micro-structural phenomena in granular shear zones

The paper deals with some characteristic phenomena of fundamental nature which occur within shear zones in granular materials. Phenomena such as self-organizing force chain networks, vortices, alternating contractant and dilatant regions within shear zones were modelled numerically using discrete element method DEM. Discrete simulations were carried out with medium-dense sand during direct a shearing test.

Modeling of the Behavior of Granular Bodies using DEM with Contact Moments

Numerical simulations of the behavior of granular bodies were carried out using a discrete element method. Two boundary value problems were analyzed: triaxial test and a passive translation of a rigid very rough retaining wall. To simulate the behavior of real grains, spheres of a different diameter with contact moments were taken into account.

Electronic structure and rovibrational predissociation of the 21Π state in KLi

Adiabatic potential energy curves of the 31Σ+, 33Σ+, 21Π and 23Π states correlating for large internuclear distance with the K(4s) + Li(2p) atomic asymptote were calculated. Very good agreement between the calculated and the experimental curve of the 21Π state allowed for a reliable description of the dissociation process through a small (∼20 cm-1 for J = 0) potential energy barrier. The barrier supports several rovibrational quasi-bound states and explicit time evolution of these states via the time-dependent nuclear Schrödinger equation, showed that the state populations decay exponentially in time. We were able to precisely describe the time-dependent dissociation process of several rovibrational levels and found that our calculated spectrum match very well with the assigned experimental spectrum. Moreover, our approach is able to predict the positions of previously unassigned lines, particularly in the case of their low intensity.

Investigations of Vortex-Structures in Granular Bodies Based on DEM and Helmholtz-Hodge Flow Field Decomposition

The paper presents some two-dimensional simulation results of vortex-structures in cohesionless initially dense sand during a quasi-static passive wall translation. The sand behaviour was simulated using the discrete element method (DEM). Sand grains were modelled by spheres with contact moments to approximately capture the irregular grain shape. In order to detect vortex-structures, the Helmholtz-Hodge decomposition of a flow displacement field from DEM calculations was used. This approach enabled us to distinguish both incompressibility and vorticity in the granular displacement field.

Discrete Modelling of Micro-structural Phenomena in Granular Shear Zones

The micro-structure evolution in shear zones in cohesionless sand for quasi-static problems was analyzed with a discrete element method (DEM). The passive sand failure for a very rough retaining wall undergoing horizontal translation towards the sand backfill was discussed. To simulate the behaviour of sand, the spherical discrete model was used with elements in the form of rigid spheres with contact moments.

Lattice Discrete Model

The chapter describes a novel discrete lattice model taking material micro-structure into account to simulate fracture in plain and fibrous concrete. Numerical results on the basis of a discrete lattice model are demonstrated for different quasi-static boundary value problems involving a fracture process in plain concrete and fibrous concrete. Numerical results are qualitatively compared with corresponding laboratory tests. Results of detailed parametric studies are demonstrated.

Comparative Modeling of Shear Localization in Granular Bodies with FEM and DEM

The intention of the paper is to compare the calculations of shear zones in granular bodies using two different approaches: a continuum and a discrete one. In the first case, the FEM based on a micro-polar hypoplastic constitutive law was used. In the second case, the DEM was taken advantage of, where contact moments were taken into account to model grain roughness. The comparative calculations were performed for a passive case of a translating and rotating retaining wall.