Surface roughness has a huge impact on many important phenomena. The most property of rough surfaces is the surface power spectrum C(q). We present spectra practical importance, obtained from height profile measured using optical methods and atomic force microscope. show how determines contact area between two solids. also applications to sealing, rubber friction adhesion for surfaces, where enters as an input.

Probing the lowest energy configuration of a complex system by quantum annealing was recently found to be more effective than its classical, thermal counterpart. Comparing classical and Monte Carlo protocols on random two-dimensional Ising model we confirm superiority relative annealing. We also propose theory annealing, based cascade Landau-Zener tunneling events. For both residual after is inversely proportional power logarithm time, but case has larger which makes it faster

The physics of sliding friction is gaining impulse from nanoscale and mesoscale experiments, simulations, theoretical modeling. This Colloquium reviews some recent developments in modeling atomistic simulation friction, covering open-ended directions, unconventional nanofrictional systems, unsolved problems.

Abstract Many well known difficulties associated with the use of two-body forces for description metallic systems may be overcome by using an expression total energy form V = ½Σ ij φ(r ) + Σ i U(ni), where n Σiρ(r is a generalized atomic coordination. The three functions φ(r), U(n) and ρ(r) are constructed empirically, fitting several physical quantities including thermal surface properties. This simple many-body force scheme can used in molecular-dynamics simulations few overheads compared...

The phase diagrams of water and ammonia were determined by constant pressure ab initio molecular dynamic simulations at pressures (30 to 300 gigapascal) temperatures (300 7000 kelvin) relevance for the middle ice layers giant planets Neptune Uranus. Along planetary isentrope behave as fully dissociated ionic, electronically insulating fluid phases, which turn metallic exceeding kelvin 5500 ammonia. At lower temperatures, exhibit a superionic solid between ionic liquid. These improve our...

We present extensive molecular-dynamics simulations of small gold particles N=100--900 atoms. use a many-body interatomic potential proven accuracy for surfaces. Structural properties are determined with various annealing strategies. Our results provide the first time microscopic description melting transition metal clusters, revealing in particular formation liquid skin as precursor effect N>350. The experimentally observed sharp decrease temperature decreasing size is recovered....

Using quantum Monte Carlo and finite-size scaling for the Hubbard model, we find evidence of a zero-temperature transition between nonmagnetic semi-metal an antiferromagnetic insulator in 2D honeycomb lattice nontrivial value U/t = 4.5 ± 0.5. The corresponding Hartree-Fock mean field is at 2.23, which indicates importance fluctuations. This represents first example Mott-Hubbard bipartite lattice. Similar transitions are predicted special lattices higher dimensions, particular 3D diamond

We study the structure of reconstructed Au (100) surface, using a phenomenological Hamiltonian, including many-body force term (the "glue"), carefully optimized to account for vast variety properties solid and liquid gold. The optimal atomic configuration slabs is obtained by molecular-dynamics strategy. find that glue drives reconstruction into denser, quasitriangular surface layer. By variation cell size atom number, lowest-energy found be roughly (1\ifmmode\times\else\texttimes\fi{}5),...

We review here some recent work in the field of quantum annealing, alias adiabatic computation. The idea annealing is to perform optimization by a evolution which tracks ground state suitable time-dependent Hamiltonian, where 'ℏ' slowly switched off. illustrate several applications strategies, starting from textbook toy-models—double-well potentials and other one-dimensional examples, with without disorder. These examples display clear way crucial differences between classical annealing....

Magnetic tunnel junctions (MTJs), composed of two ferromagnetic electrodes separated by a thin insulating barrier layer, are currently used in spintronic devices, such as magnetic sensors and random access memories. Recently, driven demonstrations ferroelectricity at the nanoscale, thin-film ferroelectric barriers were proposed to extend functionality MTJs. Due sensitivity conductance magnetization alignment (tunnelling magnetoresistance) polarization orientation electroresistance), these...

Detailed experimental results have been obtained on the reflectivity of both natural and pyrolytic graphite single crystals in visible ultraviolet regions. Results taken for $E\ensuremath{\perp}c$ $E\ensuremath{\parallel}c$ at near-normal incidence, as a function angle incidence radiation having its electric vector perpendicular parallel to plane incidence. These latter results, used conjunction with an analysis Fresnel relations anisotropic materials, permit extremely accurate values...

Abstract A review of the available electrical and structural data on both pure doped 1T-TaS2 leads us to propose that nearly commensurate transition at 200 K is accompanied by Mott localization in two dimensions. One electron out 13 Ta plane localized onto centre a star atoms. The picture helps understanding concentration dependence low-temperature resistivity cation-doped samples, particularly sharp maximum an atomic fraction x ∼ 0.08 for Ti doping. Examining recent Di Salvo Graebner (1977)...

Friction at highly lubric interfaces of two-dimensional materials is important yet incompletely characterized. This Colloquium discusses sliding and pinning between layers, using simulations twisted graphene as a prototypical system. The resulting insights are potential relevance for larger category bilayer multilayer systems well.

The bulk properties of iron at the pressure and temperature conditions Earth's core were determined by a method that combines first-principles classical molecular dynamic simulations. theory indicates (i) melting inner-core boundary (ICB) (330 gigapascals) is 5400 (+/-400) kelvin; (ii) liquid ICB about 6% denser than outer core; (iii) shear modulus solid close to its line 140 gigapascals, consistent with seismic value for inner core. These results reconcile estimates based on sound velocity...

We performed scanning-tunneling-microscopy (STM) experiments on cleaved graphite surfaces. STM clearly distinguishes between the inequivalent carbon sites, and yields an energy selective density-of-states corrugation in qualitative agreement with recent theory. A lateral resolution of better than 2 Å was achieved. The further confirm directly atomic flatness some thousand ångstrom size areas graphite.

We discuss the possible application of scanning tunneling microscope (STM) to surface electronic spectroscopy, with an explicit calculation voltage-dependent current for ideal STM experiment performed on graphite. study how and bulk states are reflected in J-V spectra, show that empty graphite may be well discriminated against bulklike structures by considering spectra at different tip-surface separations.

Computer simulations suggest that ultrathin metal wires should develop exotic, non-crystalline stable atomic structures, once their diameter decreases below a critical size of the order few spacings. The new whose details depend upon material and wire thickness, may be dominated by icosahedral packings. Helical, spiral-structured with multi-atom pitches are also predicted. phenomenon, analogous to appearance other shapes in small clusters, can rationalized terms surface energy anisotropy...

Multishell helical gold nanowires were recently imaged by electron microscopy. We show theoretically that the contact with tips at either end of wire plays a crucial role and local minima in string tension rather than total free energy determine nanowire stability. Density functional electronic structure calculations simplest thinnest coaxial silver wires variable radius chirality carried out. found minimum for single-tube is chiral consists seven strands, striking agreement observation. In...

High-temperature superconductivity in doped Mott insulators such as the cuprates contradicts conventional wisdom that electron repulsion is detrimental to superconductivity. Because fullerene conductors are also strongly correlated, recent discovery of high-critical-temperature, presumably s-wave, C60 field effect devices even more puzzling. We examine a dynamical mean-field solution model for electron-doped fullerenes shows how strong correlations can indeed enhance close transition. argue...

We study the influence of surface roughness on adhesion elastic solids. Most real surfaces have many different length scales, and this fact is taken into account in our analysis. consider detail case when can be described as a self-affine fractal, show that fractal dimension Df>2.5, force may vanish, or at least strongly reduced. block-substrate pull-off function roughness, find partial detachment transition preceding full one. The theory good qualitative agreement with experimental data.