Universal Pairwise Interatomic van der Waals Potentials Based on Quantum Drude Oscillators.

Repulsive short-range and attractive long-range van der Waals (vdW) forces play an appreciable role in the behavior of extended molecular systems. When using empirical force fields, the most popular computational methods applied to such systems, vdW forces are typically described by Lennard-Jones-like potentials, which unfortunately have a limited predictive power. Here, we present a universal parameterization of a quantum-mechanical vdW potential, which requires only two free-atom properties─the static dipole polarizability α1 and the dipole-dipole C6 dispersion coefficient. This is achieved by deriving the functional form of the potential from the quantum Drude oscillator (QDO) model, employing scaling laws for the equilibrium distance and the binding energy, and applying the microscopic law of corresponding states. The vdW-QDO potential is shown to be accurate for vdW binding energy curves, as demonstrated by comparing to the ab initio binding curves of 21 noble-gas dimers. The functional form of the vdW-QDO potential has the correct asymptotic behavior at both zero and infinite distances. In addition, it is shown that the damped vdW-QDO potential can accurately describe vdW interactions in dimers consisting of group II elements. Finally, we demonstrate the applicability of the atom-in-molecule vdW-QDO model for predicting accurate dispersion energies for molecular systems. The present work makes an important step toward constructing universal vdW potentials, which could benefit (bio)molecular computational studies.

Optimized Quantum Drude Oscillators for Atomic and Molecular Response Properties.

The quantum Drude oscillator (QDO) is an efficient yet accurate coarse-grained approach that has been widely used to model electronic and optical response properties of atoms and molecules as well as polarization and dispersion interactions between them. Three effective parameters (frequency, mass, and charge) fully characterize the QDO Hamiltonian and are adjusted to reproduce response properties. However, the soaring success of coupled QDOs for many-atom systems remains fundamentally unexplained, and the optimal mapping between atoms/molecules and oscillators has not been established. Here we present an optimized parametrization (OQDO) where the parameters are fixed by using only dipolar properties. For the periodic table of elements as well as small molecules, our model accurately reproduces atomic (spatial) polarization potentials and multipolar dispersion coefficients, elucidating the high promise of the presented model in the development of next-generation quantum-mechanical force fields for (bio)molecular simulations.

Electronic properties of graphene oxide: nanoroads towards novel applications.

In this work, we suggest an approach to manipulate the electronic properties of graphene oxide in a controllable manner. We study graphene nanoroads paved inside graphene oxide using density functional calculations. We show that this patterning allows transforming an insulator, graphene oxide, into a semiconductor or metal depending on the orientation of the nanoroads and their magnetic state. As a semiconductor, patterned graphene oxide is characterized by notably low effective masses of charge carriers. Additionally, we demonstrate the possibility to force the transition from a semiconducting to a half-metallic state in a controllable manner, by application of an external electric field. We believe that this remarkable opportunity to combine and control the electronic and magnetic properties of a material within a single sheet of graphene oxide paves the way towards new applications of graphene-oxide-based devices in 2D optoelectronics and spintronics.