Anharmonic Vibrational States of Double-Well Potentials in the Solid State from DFT Calculations.

We introduce a general approach for the simulation of quantum vibrational states of (symmetric and asymmetric) double-well potentials in molecules and materials for thermodynamic and spectroscopic applications. The method involves solving the nuclear Schrödinger equation associated with a one-mode potential of the type () = + + (with < 0 and > 0) and thus explicitly includes nuclear quantum effects. The potential, (), is obtained from density functional theory (DFT) calculations performed at displaced nuclear configurations along the selected normal mode, .

Accelerated linear algebra for large scale DFT calculations of materials on CPU/GPU architectures with CRYSTAL.

We discuss the implementation strategy, numerical accuracy, and computational performance of the acceleration of linear algebra operations through graphics processing units (GPUs) for the self-consistent field driver of the Crystal electronic structure package for solid state density functional theory simulations. Accelerated tasks include matrix multiplication, diagonalization, and inversion, as well as Cholesky decomposition. The scaling of the implemented strategy over multiple accelerating devices is assessed in the range of 1-8 GPUs per node and found to be remarkably regular.

The Electron-Density Distribution of UCl and Its Topology from X-ray Diffraction.

The chemistry of electrons in actinide complexes and materials is still poorly understood and represents a serious challenge and opportunity for experiment and theory. The study of the electron density distribution of the ground state of such systems through X-ray diffraction represents a unique opportunity to quantitatively investigate different chemical bonding interactions at once, but was considered "almost impossible" on heavy-atom systems, until very recently. Here, we present a combined experimental and theoretical investigation of the electron density distribution in UCl_ crystals and comparison with the previously reported spin density distribution from polarized neutron diffraction.