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Oct 5, 2013
10/13

by
Dominik Marx

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An introduction into the basic ideas of ab initio molecular dynamics methods is given. These methods unify molecular dynamics simulations and electronic structure calculations in the sense that the interactions, i.e. the forces used to propagate the classical nuclei, are obtained from concurrent or �on the fly� electronic structure calculations. Several such molecular dynamics schemes are discussed which arise from a sequence of approximations to the fully coupled Schr ̈odinger equation...

Topics: Molecular Dynamics, "

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Sep 19, 2013
09/13

by
B. Meyer; Dominik Marx

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An extensive theoretical investigation of the nonpolar (10$\bar{1}$0) and (11$\bar{2}$0) surfaces as well as the polar zinc terminated (0001)--Zn and oxygen terminated (000$\bar{1}$)--O surfaces of ZnO is presented. Particular attention is given to the convergence properties of various parameters such as basis set, k--point mesh, slab thickness, or relaxation constraints within LDA and PBE pseudopotential calculations using both plane wave and mixed basis sets. The pros and cons of different...

Source: http://arxiv.org/abs/cond-mat/0206549v1

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Sep 23, 2013
09/13

by
Matteo Farnesi Camellone; Dominik Marx

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Water, the ubiquitous solvent, is also prominent in forming liquid solid interfaces with catalytically active surfaces, in particular with promoted oxides. We study the complex interface of a gold nanocatalyst, pinned by an F center on titania support, and water. The ab initio simulations uncover the microscopic details of solvent-induced charge rearrangements at the metal particle. Water is found to stabilize charge states differently from the gas phase as a result of structure specific charge...

Source: http://arxiv.org/abs/1303.5235v1

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Sep 21, 2013
09/13

by
Piotr M. Kowalski; Bernd Meyer; Dominik Marx

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A comprehensive phase diagram of lowest-energy structures and compositions of the rutile TiO_2(110) surface in equilibrium with a surrounding gas phase at finite temperatures and pressures has been determined using density functional theory in combination with a thermodynamic formalism. The exchange of oxygen, hydrogen, and water molecules with the gas phase is considered. Particular attention is given to the convergence of all calculations with respect to lateral system size and slab...

Source: http://arxiv.org/abs/0902.0854v1

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Sep 18, 2013
09/13

by
Roger Rousseau; Eduard Schreiner; Axel Kohlmeyer; Dominik Marx

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A joint experimental / theoretical investigation of the elastin-like octapeptide GVG(VPGVG) was carried out. In this paper a comprehensive molecular dynamics study of the temperature dependent folding and unfolding of the octapeptide is presented. The current study, as well as its experimental counterpart find that this peptide undergoes an "inverse temperature transition", ITT, leading to a folding at about 310-330 K. In addition, an unfolding transition is identified at unusually...

Source: http://arxiv.org/abs/q-bio/0401012v1

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40

Jul 20, 2013
07/13

by
Matteo Farnesi Camellone; Piotr M. Kowalski; Dominik Marx

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Extensive first principles calculations are carried out to investigate gold-promoted TiO2(110) surfaces in terms of structure optimizations, electronic structure analyses, ab initio thermodynamics calculations of surface phase diagrams, and ab initio molecular dynamics simulations. All computations rely on density functional theory in the generalized gradient approximation (PBE) and account for on-site Coulomb interactions via inclusion of a Hubbard correction, PBE+U, where U is computed from...

Source: http://arxiv.org/abs/1107.0840v1

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Sep 18, 2013
09/13

by
A. Daniel Boese; Amalendu Chandra; Jan M. L. Martin; Dominik Marx

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The ammonia dimer (NH3)2 has been investigated using high--level ab initio quantum chemistry methods and density functional theory (DFT). The structure and energetics of important isomers is obtained to unprecedented accuracy without resorting to experiment. The global minimum of eclipsed C_s symmetry is characterized by a significantly bent hydrogen bond which deviates from linearity by about 20 degrees. In addition, the so-called cyclic C_{2h} structure is extremely close in energy on an...

Source: http://arxiv.org/abs/physics/0306154v1

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Sep 21, 2013
09/13

by
Piotr M. Kowalski; Matteo Farnesi Camellone; Nisanth N. Nair; Bernd Meyer; Dominik Marx

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The dynamics of an F--center created by an oxygen vacancy on the $\mathrm{TiO_{2}(110)}$ rutile surface has been investigated using {\it ab initio} molecular dynamics. These simulations uncover a truly complex, time-dependent behavior of fluctuating electron localization topologies in the vicinity of the oxygen vacancy. Although the two excess electrons are found to populate preferentially the second subsurface layer, they occasionally visit surface sites and also the third subsurface layer....

Source: http://arxiv.org/abs/1008.4652v1