Spin-orbit split two-dimensional states of BiTeI/Au(1 1 1) interfaces.

We present an ab initio study of interfaces formed by placing a single trilayer of BiTeI on the Au(1 1 1) surface. We consider two possible interfaces with the parallel and antiparallel orientation of the trilayer dipole moment with respect to the surface normal, i.e. Te-Bi-I/Au(1 1 1) and I-Bi-Te/Au(1 1 1). We show that the resulting interface state that originates from the modified spin-orbit split surface state of the clean Au(1 1 1) surface resides at high energy above the Fermi level and acquires a large spin-splitting and reversal helicity as compared with the original surface state. The former lowest conduction state of the trilayer, which is one of the hitherto known giant Rashba spin-split states of few-atomic-layer structures, becomes partly occupied. In the I-Bi-Te/Au(1 1 1) interface, this state represents a Rashba system with strong spin-orbit interaction, where the outer branch of the spin-split state is mostly populated.

Structure and vibrational properties of the PTCDA/Ag(1 1 1) interface: bilayer versus monolayer.

The structural and vibrational properties of metal-organic interfaces have been examined by means of infrared (IR) absorption spectroscopy and density functional theory (DFT) with an approach accounting for long-range dispersive interactions. We focus on a comparative study of the PTCDA monolayer and bilayer on Ag(1 1 1). The equilibrium geometry at the molecule-metal interface and the IR spectrum of the chemisorbed monolayer of PTCDA on Ag(1 1 1) are well described by the computations. In the bilayer structure, the presence of a physisorbed adlayer on top of PTCDA/Ag(1 1 1) presents a challenge for DFT. As previously described for other systems, the polarization of the substrate is not captured correctly and results in too low energies of frontier molecular orbitals. This results in an apparent contribution from the vibrations of second-layer PTCDA to the IR spectrum due to interfacial dynamical charge transfer processes. After removing these peaks with artificially strong intensity, calculated and experimental data show good agreement and the IR spectrum can be described as the sum of the spectra of the PTCDA/Ag(1 1 1) contact layer and a physisorbed PTCDA monolayer on top.

The characteristics of super-elastic Ni-Ti wires in three-point bending. Part I: The effect of temperature.

The load-deflection behaviour of a number of commercially available superalloy nickel-titanium orthodontic wires has been examined in three-point bending over the temperature range 5-50 degrees C. The loading and unloading curves and plateau regions are found to be closely related to temperature with the stiffness decreasing quite dramatically over a narrow temperature range. The position of this range depends on the material being tested as there are marked differences due to the differing processing methods of the manufacturer. Force values at mouth temperature can differ by 600 per cent for wires of the same nominal diameter made by different manufacturers.

The characteristics of super-elastic Ni-Ti wires in three-point bending. Part II: Intra-batch variation.

Intra-batch variation in the load-deflection characteristics of 13 superalloy nickel-titanium wires has been examined at nominal mouth temperature (35 degrees C). The results indicate that although most of the superalloy nickel-titanium wires were undersized, the variation in diameter within a batch was of the same order as that reported for 18/8 stainless steel wire. The largest coefficients of variation for the intra-batch variation for the initial slope and the unloading plateau values were found to be approximately 7.5 and 10 per cent, respectively. A high degree of correlation was found between the mean slopes of the initial load-deflection curve in three-point bending at 35 degrees C and the mean wire diameter raised to the fourth power for the 13 superalloys wires, from which a value for Young's modulus (E) of 55.4 GPa was deduced on the basis that at this temperature the wires will have an austenitic structure and virtually identical compositions.