Off-lattice pattern recognition scheme for KMC simulations

We report the development of a pattern-recognition scheme for the off-lattice self-learning kinetic Monte Carlo (KMC) method, one that is simple and flexible enough that it can be applied to all types of surfaces. In this scheme, to uniquely identify the local environment and associated processes involving three-dimensional (3D) motion of an atom or atoms, … Read more

Selective oxidation of ammonia on RuO2(110)

We have used a combination of density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations to calculate the reaction rates for the selective oxidation of ammonia on RuO2(110). Our KMC simulations of 18 reactions among NHx (x=0-3) and OHx (x=0-2) species on RuO2(110) show 93% selectivity for NO, in close agreement with experiment (~95%). The chief … Read more

Time-dependent density-matrix functional theory for biexcitonic phenomena

We formulate a time-dependent density-matrix functional theory (TDDMFT) approach for higher-order correlation effects like biexcitons in optical processes in solids based on a reduced two-particle density-matrix formalism within the normal orbital representation. A TDDMFT version of the Schrodinger equation for biexcitons in terms of one- and two-body reduced density matrices is derived, which leads to … Read more

Toward an Understanding of Ligand Selectivity in Nanocluster Synthesis

We performed scalar relativistic density functional theory (DFT) calculations using the projector augmented wave scheme (PAW) to examine the reactivity and selectivity of diphosphine ligands LM, with the formula PH2(CH2)MPH2 (spacer M = 3, 5), toward small-sized cationic Aun (n = 7-11) nanoclusters. By isolating the ligand-induced contribution to the stability condition, we show that such interaction … Read more

A Surface Coordination Network Based on Substrate-Derived Metal Adatoms with Local Charge Excess

We present a coordination network, formed at a metal surface in a system facile to prepare because the required metal centers can be released in a measured fashion from the substrate by simple annealing. Analysis of the charge density in this system suggests that metal adatoms can have a pronounced donating character despite the electron … Read more

A DFT+DMFT approach for nanosystems

We propose a combined density-functional-theorydynamical-mean-field-theory (DFT + DMFT) approach for reliable inclusion of electronelectron correlation effects in nanosystems. Compared with the widely used DFT + U approach, this method has several advantages, the most important of which is that it takes into account dynamical correlation effects. The formalism is illustrated through different calculations of the … Read more

Effect of dipolar interactions on the magnetization of a cubic array of nanomagnets

We investigated the effect of intermolecular dipolar interactions on an ensemble of 100 three-dimensional systems of 5�5�4 nanomagnets, each with spin S=5, arranged in a cubic lattice. We employed the Landau-Lifshitz-Gilbert equation to solve for the magnetization curves for several values of the damping constant, the induction sweep rate, the lattice constant, the temperature, and … Read more