During the past decade, computer simulations based on a quantum-mechanical description of the interactions between electrons and between electrons and atomic nuclei have developed an increasingly important impact on solid-state physics and chemistry and on materials science—promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within density-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calculations and structural optimizations for systems with thousands of atoms and ab initio molecular dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mechanical and dynamical properties, liquids, glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chemical reactions, and catalysis) are reviewed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008

Ab-initio simulations of materials using VASP: Density-functional theory and beyond.

Materials for hydrogen storage

Transparent conductors as solar energy materials: A panoramic review

https://uhra.herts.ac.uk/bitstream/handle/2299/11214/904970.pdf;sequence=2

A review of solar collectors and thermal energy storage in solar thermal applications

We give a general introduction to quantum phase transitions in strongly-correlated electron systems. These transitions which occur at zero temperature when a non-thermal parameter $g$ like pressure, chemical composition or magnetic field is tuned to a critical value are characterized by a dynamic exponent $z$ related to the energy and length scales $\Delta$ and $\xi$. Simple arguments based on an expansion to first order in the effective interaction allow to define an upper-critical dimension $D_{C}=4$ (where $D=d+z$ and $d$ is the spatial dimension) below which mean-field description is no longer valid. We emphasize the role of pertubative renormalization group (RG) approaches and self-consistent renormalized spin fluctuation (SCR-SF) theories to understand the quantum-classical crossover in the vicinity of the quantum critical point with generalization to the Kondo effect in heavy-fermion systems. Finally we quote some recent inelastic neutron scattering experiments performed on heavy-fermions which lead to unusual scaling law in $\omega /T$ for the dynamical spin susceptibility revealing critical local modes beyond the itinerant magnetism scheme and mention new attempts to describe this local quantum critical point.

https://arxiv.org/pdf/cond-mat/0102119.pdf

Quantum Phase Transitions

A new antiferromagnetic phase in EuSe below 1.8 K

The existence of dissociation plateaus in the pressure-composition isotherms for hydrogen absorption in amorphous metals is shown to depend on the degree of configurational disorder in the host lattice Within a mean-field approximation for the attractive elastic hydrogen-hydrogen interaction, the Stoner-type condition $\ensuremath{-}an({E}_{0})\ensuremath{\ge}1$ is derived for the existence of a positive critical temperature ${T}_{c}$ [$a$ is a measure of the strength of the effective hydrogen-hydrogen interaction and $n({E}_{0})$ is the maximum of the symmetric density-of-sites function $n(E)$ which describes the spread in the energy of the sites which can be occupied by hydrogen atoms] Analytical expressions for ${T}_{c}$ are derived for a square and a doublesquare density-of-sites function These simple models for $n(E)$ are used to reproduce experimental results on crystalline and amorphous nickel-zirconium hydrides

/pdf/phase-separation-in-amorphous-metal-hydrides-a-stoner-type-2wv75xgp18.pdf

Phase separation in amorphous metal hydrides: A Stoner-type criterion

Nanoconfined MgH2 is destabilized compared to its bulk counterpart because of an interface energy effect. The hydrogen equilibrium pressure increases by an order of magnitude when decreasing the Mg layer thickness from 10 to 2 nm. This relates to an interface energy change of 0.3 J m−2.

Interface Energy Controlled Thermodynamics of Nanoscale Metal Hydrides

Optimization of Mg-based fiber optic hydrogen detectors by alloying the catalyst

We describe an experimental method for in situ resistivity measurements during the electrochemical hydrogen loading of thin, switchable metal hydride films. Using an oxygen-free electrolyte we are able to measure the hydrogen concentration in the films quantitatively and to determine the pressure-composition isotherms and the hydrogen concentration dependence of the resistivity. Furthermore, the optical properties can be investigated by simultaneous transmission and reflection spectroscopy. The power of these in situ measurements is discussed on the basis of results obtained on YHx films; possibilities for additional experiments are briefly described

R.P. Griessen

Papers

A new antiferromagnetic phase in EuSe below 1.8 K

Phase separation in amorphous metal hydrides: A Stoner-type criterion

Interface Energy Controlled Thermodynamics of Nanoscale Metal Hydrides

Optimization of Mg-based fiber optic hydrogen detectors by alloying the catalyst

In Situ Resistivity Measurements and Optical Transmission and Reflection Spectroscopy of Electrochemically Loaded Switchable YHx Films