Table of contents

We propose a quantum oscillation experiment by which the rotation of an underdoped YBa₂Cu₃O_6+x sample about two different axes with respect to the orientation of the magnetic field can be used to infer the shape of the in-plane cross-section of corrugated Fermi surface cylinder(s). Deep corrugations in the Fermi surface are expected to give rise to nodes in the quantum oscillation amplitude that depend on the magnitude and orientation of the magnetic induction B. Because the symmetries of electron and hole cylinders within the Brillouin zone are expected to be very different, the topology can provide essential clues as to the broken symmetry responsible for the observed oscillations. The criterion for the applicability of this method to the cuprate superconductors (as well as other layered metals) is that the difference in quantum oscillation frequency 2ΔF between the maximum (belly) and minimum (neck) extremal cross-sections of the corrugated Fermi surface exceeds |B|.

By means of neutron scattering we show that the high temperature precursor to the hidden order state of the heavy fermion superconductor URu₂Si₂ exhibits heavily damped incommensurate paramagnons whose strong energy dispersion is very similar to that of the long-lived longitudinal f spin excitations that appear below T₀. This suggests that there is a strongly hybridized character to the itinerant excitations observed previously above the hidden order transition. Here we present evidence that the itinerant excitations, like those in chromium, are due to Fermi surface nesting of hole and electron pockets; hence the hidden order phase probably originates from a Fermi surface instability. We identify wavevectors that span nested regions of a f–d hybridized band calculation and that match the neutron spin crossover from incommensurate to commensurate on approach to the hidden order phase.

We have measured the strain dependent transport properties of phase separated manganite thin films. We subjected (La_1−yPr_y)_1−xCa_xMnO₃ thin films grown on NdGaO₃(110) substrates to direct external mechanical stress using a three-point beam bending method. The resultant change in resistance reveals a colossal piezoresistance (CPR) in manganites. Our experiments reveal that phase separation is a necessary but not sufficient condition for CPR. The maximum CPR is observed only when the phase boundaries are free to move in the fluid-like phase separated state. Our results show that both long-range strain interactions and quenched disorder play an important role in micrometer scale phase separation in manganites, albeit in different temperature ranges.

When a local potential changes abruptly in time, an electron gas responds by shifting to a new state which at long times is orthogonal to the one in the absence of the local potential. This is known as Anderson's orthogonality catastrophe and it is relevant for the so-called x-ray edge or Fermi-edge singularity, and for tunneling into an interacting one-dimensional system of fermions. It often happens that the finite frequency response of the photon absorption or the tunneling density of states exhibits a singular behavior as a function of frequency: , where ω_th is a threshold frequency and α is an exponent characterizing the singular response. In this review singular responses of spin-incoherent Luttinger liquids are reviewed. Such responses most often do not fall into the familiar form above, but instead typically exhibit logarithmic corrections and display a much higher universality in terms of the microscopic interactions in the theory. Specific predictions are made, the current experimental situation is summarized and key outstanding theoretical issues related to spin-incoherent Luttinger liquids are highlighted.

We report a theoretical study of hydroxyl vacancies in aluminosilicate and aluminogermanate single-walled metal-oxide nanotubes. Defects are introduced on both sides of the tube walls and lead to occupied and empty states in the band gap which are highly localized both in energy and in real space. Different magnetization states are found depending on both the chemical composition and the specific side with respect to the tube cavity. The defect-induced perturbations to the pristine electronic structure are related to the electrostatic polarization across the tube walls and the ensuing change in Lewis acid–base reactivity. A general approach towards a quantitative evaluation of both the polarization across the tube walls and the tube excluded volume is also proposed and discussed on an electrostatic basis.

The transfer of an electron from a carbon nanotube (CNT) tip into vacuum under a high electric field is considered beyond the usual one-dimensional semi-classical approach. A model of the potential energy outside the CNT cap is proposed in order to show the importance of the intrinsic CNT parameters such as radius, length and vacuum barrier height. This model also takes into account set-up parameters such as the shape of the anode and the anode-to-cathode distance, which are generically portable to any modelling study of electron emission from a tip emitter. Results obtained within our model compare well to experimental data. Moreover, in contrast to the usual one-dimensional Wentzel–Kramers–Brillouin description, our model retains the ability to explain non-standard features of the process of electron field emission from CNTs that arise as a result of the quantum behaviour of electrons on the surface of the CNT.

We study theoretically acoustic phonon modes in nanowire superlattices (NWSLs) composed of cubic materials. We classify the acoustic phonon modes in rectangular and square cross-section NWSLs, based on group theory. For NWSLs consisting of GaAs and AlAs, we calculate numerically the dispersion relations of each phonon mode and corresponding displacement fields. We examine the effects of both the lateral confinement and superlattice modulation along the wire axis. The results suggest that peculiar electron–phonon interactions occur because the vibrations of both the lateral and longitudinal confining potentials induce scattering potential in addition to the deformation and piezoelectric potentials.

The effects of inelastic interactions between current-carrying electrons and vibrational modes of a nanoscale junction are a major limiting factor on the stability of such devices. A method for dynamical simulation of inelastic electron–ion interactions in nanoscale conductors is applied to a model system consisting of an adatom bonded to an atomic wire. It is found that the vibrational energy of such a system may decrease under bias, and furthermore that, as the bias is increased, the rate of cooling, within certain limits, will increase. This phenomenon can be understood qualitatively through low-order perturbation theory, and is due to the presence of an anti-resonance in the transmission function of the system at the Fermi level. Such current-assisted cooling may act as a stabilization mechanism, and may form the basis for a nanoscale cooling 'fan'.

Using first principles total energy calculations within the full potential linearized augmented plane wave (FP-LAPW) method, we have investigated the structural, electronic, thermodynamic and optical properties of Pb_1−xCa_xS, Pb_1−xCa_xSe and Pb_1−xCa_xTe ternary alloys. The effect of composition on lattice parameter, bulk modulus, band gap, refractive index and dielectric function was investigated. Deviations of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence were observed for the three alloys. Using the approach of Zunger and co-workers, the microscopic origins of band gap bowing have been detailed and explained. The disorder parameter (gap bowing) was found to be mainly caused by the chemical charge transfer effect. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ΔH_m, as well as the phase diagram. It was shown that all of these alloys are stable at low temperature. The calculated refractive indices and optical dielectric constants were found to vary nonlinearly with Ca composition.

The atomic response of the topmost graphene layer on graphite was studied by using scanning tunneling microscopy (STM) as a function of tunneling gap distance, gap voltage and bias polarity. The contrast of the site-dependent topographical image depends on the gap distance, and the site-dependent tunneling current order of magnitude at a given gap distance is switched with the gap voltage (i.e. the contrast is significantly altered). The site-dependent current order is altered at the lower positive gap voltage as the gap distance is reduced between the probe and the carbon atoms of the topmost graphene layer. The switching in the atomic image contrast and the current order of magnitude is directly related to the differential atomic response of carbon atoms to the STM probe originating from the electronically active and mechanically soft β-carbon atoms.

A comprehensive investigation of oxygen vacancy and interstitial diffusion in ZnO has been performed using ab initio total energy calculations with both the local density approximation (LDA) and the generalized gradient approximation (GGA). Based on our calculation results, oxygen octahedral interstitials are fast diffusers, contributing to annealing processes, as well as being responsible for the self-diffusion of oxygen for n-type ZnO, and oxygen vacancies are responsible for the self-diffusion of oxygen for p-type ZnO.

We studied lithium azide (LiN₃) by x-ray diffraction and Raman spectroscopy at hydrostatic compression up to pressures above 60 GPa at room temperature. The results of x-ray diffraction analyses reveal the stability of the ambient-pressure C 2/m crystal structure up to the highest pressure. The pressure dependence of librational modes provides evidence for an order–disorder transition at low pressures (below 3 GPa), similar to the transition observed previously at low temperatures. The observed structure stability indicates that this transition is not associated with structural changes. The phase stability of LiN₃ is in contrast to that of sodium azide (which is isostructural at ambient pressure), for which a set of phase transitions has been reported at pressures below 50 GPa.

Using the full-potential linearized augmented plane wave method, we have investigated the oxygen vacancy defect induced ferromagnetism in both rutile and anatase TiO₂. It has been found that the oxygen vacancy induces lattice distortion in rutile TiO₂, whereas there is no such meaningful change in the anatase structure. Interestingly, the lattice distorted rutile TiO₂ shows an oxygen vacancy induced ferromagnetic state with a magnetic moment of 0.22 µ_B in the Ti atom neighboring the vacancy site, while only 0.06 µ_B is observed in the Ti atom in anatase TiO₂. We attribute the sizable magnetic moment due to the oxygen vacancy in rutile TiO₂ to the charge redistribution owing to lattice distortion. Experimentally measured magnetic hysteresis curves for undoped rutile and anatase TiO₂ films clearly display ferromagnetic behavior at room temperature. The observed magnetic strength of the rutile sample turns out to be larger than that of the anatase sample, in accordance with the theoretical calculations.

The local atomic order of an amorphous Se_0.90S_0.10 alloy produced by mechanical alloying was studied by x-ray diffraction and extended x-ray absorption fine structure (EXAFS) data obtained at three temperatures, T = 300, 200 and 30 K. From the cumulant analysis of the EXAFS data, structural properties such as average interatomic distances, average coordination numbers, Debye–Waller factors and anharmonicity, given by the third cumulant, were obtained. The results found indicate that there is alloying at an atomic level, and Se–S pairs are more disordered and distorted than Se–Se ones due to the milling process.

We develop a model for the reflection and transmission of plane waves by an isotropic layer sandwiched between two uniaxial crystals of arbitrary orientation. In the laboratory frame, reflection and transmission coefficients corresponding to the principal polarization directions in each crystal are given explicitly in terms of the axis and propagation directions. The solution is found by first deriving explicit expressions for reflection and transmission amplitude coefficients for waves propagating from an arbitrarily oriented uniaxial anisotropic material into an isotropic material. By combining these results with Lekner's (1991 J. Phys.: Condens. Matter3 6121–33) earlier treatment of waves propagating from isotropic media to anisotropic media and employing a matrix method we determine a solution to the general form of the multiple reflection case. The example system of a wetted interface between two ice crystals is used to contextualize the results.

We study structural transitions in a system of interacting particles arranged as a crystalline bilayer, as a function of the density ρ and the distance d between the layers. As d is decreased a sequence of transitions involving triangular, rhombic, square and centred rectangular lattices is observed. The sequence of phases and the order of transitions depends on the nature of the interactions.

The crystal structure, dc and ac magnetic susceptibility, electron spin resonance and magnetoresistive behavior of Nd_xBi_0.5−xSr_0.5MnO₃ (x = 0.1, 0.2, 0.3 and 0.4) compounds are studied. The Rietveld analysis of the XRD data shows that the samples crystallize in an orthorhombic perovskite structure, with Pbnm space group for x = 0.1 and 0.2 and Imma space group for x = 0.4 and 0.3. Magnetic studies reveal that substituting Bi with Nd collapses the robust charge ordered AFM state of Bi_0.5Sr_0.5MnO₃ to an inhomogeneous magnetic state. As Nd concentration increases there is a gradual appearance of cluster glass behavior. ESR studies reveal that the NBSMO system phase separates into ferromagnetic and antiferromagnetic regions below the transition temperature.

Computation of the observables of a Mössbauer spectrum, primarily the isomer shift, from a first-principles approach is described. The framework used is density functional theory using the projector augmented wave formalism (DFT PAW), which enables efficient computation even of many-electron solids such as SnCl₂. The proper PAW version of the isomer shift is derived and shown to be correct through comparison of computed shifts and experiment in a variety of compounds based on tin, germanium and zinc. The effects of pressure are considered as well as motional effects including the Lamb–Mössbauer factor and the second-order Doppler shift.

Sr₂FeMoO₆ oxides exhibit a half-metallic ferromagnetic (HM-FM) ground state and peculiar magnetic and magnetotransport properties, which are interesting for applications in the emerging field of spintronics and attractive for fundamental research in the field of heavily correlated electron systems. Sr₂FeWO₆ is an insulator with an antiferromagnetic (I-AFM) ground state. The solid solutions Sr₂FeMo_xW_1−xO₆ also have peculiar properties—W doping enhances chemical order which allows stabilization of the HM-FM state; as the W content exceeds a certain value a metal to insulator transition (MIT) occurs. The role of W in determining the physical properties of Sr₂FeMo_xW_1−xO₆ systems has been a matter of intense investigation. This work deals with the problem of the structural and electronic changes related to the MIT from a local perspective by means of x-ray absorption spectroscopy (XAS). This technique allows one to probe in detail the local structure and electronic modifications around selected absorber ions (W, Mo, Fe and Sr in our case). The results of XAS analysis in the whole composition range (0≤x≤1), in the near edge (XANES) and extended (EXAFS) regions, demonstrate an abrupt change of the local structure around the Fe and Mo sites at the critical composition, x_c. This change represents the microstructural counterpart associated with the MIT. Conversely, the local structure and electronic configuration of W ions remain unaltered in the whole composition range, suggesting indirect participation of W in the MIT.

We present here a generalized augmented space recursive technique which includes the effects of diagonal and environmental disorder explicitly: an analytic, lattice translational invariant, multiple scattering theory for the study of short range ordering in random ternary alloys. Our generalized augmented space formalism includes atomic correlations over a finite cluster including short range order (SRO). We propose the augmented space recursion (ASR), a computationally fast and accurate technique which incorporates configuration fluctuations over a large local environment. We apply the formalism to a tight-binding linear muffin-tin orbital (LMTO) study of stainless steel Fe_80−xNi_xCr₂₀ (x = 14 and 17). We have demonstrated the effects of short range ordering by calculating the configuration averaged density of states with and without SRO and with different kinds of cluster environment embedded in an averaged medium.

The augmented space approach to the study of random ternary alloys, described in an earlier paper (Alam and Mookerjee 2009 J. Phys.: Condens. Matter21 195503), has been combined with the generalized recursion method of Viswanath and Müller (1993 The User Friendly Recursion Method, (Troisieme Cycle de la Physique, en Suisse Romande)) and the tight-binding linear muffin-tin orbitals technique (TB-LMTO) to study the optical response in disordered Cu_xNi_yZn_z alloys, and compared with existing experimental results.

We show that the Korringa ratio, associated with nuclear magnetic resonance in metals, is unity if vertex corrections to the dynamic spin susceptibility are negligible, the hyperfine coupling is momentum independent, and there exists an energy scale below which the density of states is constant. In the absence of vertex corrections we also find a Korringa behaviour for T₁, the nuclear spin relaxation rate, i.e., , and a temperature independent Knight shift. These results are independent of the form and magnitude of the self-energy (so far as is consistent with neglecting vertex corrections) and of the dimensionality of the system.

Detailed band structure calculations have been performed for Cd₂Re₂O₇ in high-, middle- and low-temperature (T) phases. The calculations are based on the observed lattice structures from x-ray diffraction measurements. The spin–orbit interaction is incorporated self-consistently in both the generalized gradient approximation (GGA) and the GGA plus Hubbard U (GGA+U) approaches. It is found that the on-site U has negligible effects on the Re 5d band structures; therefore both the GGA and GGA+U Re 5d band energies agree well with the observed O K-edge x-ray absorption spectroscopy (XAS) spectrum, whereas the Cd 4d band energy observed from photoemission spectroscopy can only be correctly reproduced by GGA+U calculations, indicating the relatively itinerant Re 5d and localized Cd 4d electrons. On the other hand, the spin–orbit coupling gives rise to nontrivial spin and orbital magnetic moments for the middle- T phase. Most unexpectedly, we found that the low- T phase exhibits quasi-two-dimensional Fermi surfaces. The calculated carrier numbers for the three phases are, at least qualitatively, consistent with the measured Hall coefficient.

We present a study of the spin disorder resistivity () and the electronic specific heat coefficient (γ) in Gd₄(Co_1−xCu_x)₃ compounds, with x = 0.00, 0.05, 0.10, 0.20 and 0.30. The experimental results show a strongly nonlinear dependence of on the average de Gennes factor (G_av) which, in similar intermetallic compounds, is usually attributed to the existence of spin fluctuations on the Co 3d bands. Values of γ were found around 110 mJ mol⁻¹ K⁻² for the Gd₄(Co_1−xCu_x)₃ compounds, much larger than 38.4 mJ mol⁻¹ K⁻² found for the isostructural nonmagnetic Y₄Co₃ compound. Using a novel type of analysis we show that the ratio follows a well-defined linear dependence on G_av, which is expected when appropriate dependencies with the effective electron mass are taken into account. This indicates that band structure effects, rather than spin fluctuations, could be the main cause for the strong electron scattering and γ enhancement observed in the Gd₄(Co_1−xCu_x)₃ compounds. A discussion on relevant features of magnetization and electrical resistivity data, for the same series of compounds, is also presented.

We use a Green's function method to study the temperature-dependent average moment and magnetic phase-transition temperature of the striped antiferromagnetism of LaFeAsO, and other similar compounds, as the parents of FeAs-based superconductors. We consider the nearest and the next-nearest couplings in the FeAs layer, and the nearest coupling for inter-layer spin interaction. The dependence of the transition temperature T_N and the zero-temperature average spin on the interaction constants is investigated. We obtain an analytical expression for T_N and determine our temperature-dependent average spin from zero temperature to T_N in terms of unified self-consistent equations. For LaFeAsO, we obtain a reasonable estimation of the coupling interactions with the experimental transition temperature T_N = 138 K. Our results also show that a non-zero antiferromagnetic (AFM) inter-layer coupling is essential for the existence of a non-zero T_N, and the many-body AFM fluctuations reduce substantially the low-temperature magnetic moment per Fe towards the experimental value. Our Green's function approach can be used for other FeAs-based parent compounds and these results should be useful to understand the physical properties of FeAs-based superconductors.

Small angle x-ray scattering (SAXS) in a poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) solution has shown the important role of π-electron conjugation in controlling the chain conformation and assembly. By increasing the extent of conjugation from 30 to 100%, the persistence length (l_p) increases from 20 to 66 Å. Moreover, a pronounced second peak in the pair distribution function has been observed in a fully conjugated chain, at larger length scales. This feature indicates that the chain segments tend to self-assemble as the conjugation along the chain increases. Xylene enhances the rigidity of the PPV backbone to yield extended structures, while tetrahydrofuran solvates the side groups to form compact coils in which the l_p is much shorter.

Picosecond time-resolved photoluminescence from biexcitons in CuCl quantum dots (QDs) embedded in a NaCl matrix has been measured using an optical Kerr gate method. Ultrafast pulsed emission from the biexciton states was observed for the first time, only under resonant two-photon excitation of biexcitons. This implies that complete population inversion between the biexciton and exciton states is necessary in order to trigger the pulsed emission. In addition, the nature of the dependence of the time profiles of the pulsed emission on the excitation intensity reveals that the peak intensity is directly proportional to the square of the number of excited QDs. We conclude that this phenomenon is caused by superfluorescence, that is, the cooperative spontaneous radiative decay of many isolated excited states coupled by a resonant electromagnetic wave. Such a phenomenon has been observed for the first time in an ensemble of semiconductor QDs in this study. The results presented in this paper show that it is possible to control the microscopic coherent dynamics of electronic excited states in a QD ensemble.

A plasmonic terahertz detector that integrates a voltage-controlled planar barrier into a grating gated GaAs/AlGaAs high electron mobility transistor has been fabricated and experimentally characterized. The plasmonic response at fixed grating gate voltage has a full width at half-maximum of 40 GHz at ∼405 GHz. Substantially increased responsivity is achieved by introducing an independently biased narrow gate that produces a lateral potential barrier electrically in series with the resonant grating gated region. DC electrical characterization in conjunction with bias-dependent terahertz responsivity and time constant measurements indicate that a hot electron bolometric effect is the dominant response mechanism at 20 K.

Measurements of the sound velocities in a single crystal of MnSi were performed in the temperature range 4–150 K. Elastic constants, controlling propagation of longitudinal waves, reveal significant softening at a temperature of about 29.6 K and small discontinuities at ∼28.8 K, which corresponds to the magnetic phase transition in MnSi. In contrast, the shear elastic moduli do not show any softening at all, reacting only to the small volume deformation caused by the magneto-volume effect. The current ultrasonic study exposes an important fact that the magnetic phase transition in MnSi, occurring at 28.8 K, is just a minor feature of the global transformation marked by the rounded maxima or minima of heat capacity, thermal expansion coefficient, sound velocities and absorption, and the temperature derivative of resistivity.

The magnetism in graphene due to single-atom defects is examined by using spin-polarized density functional theory. The magnetic moment per defect due to substitutional atoms and vacancy defects is dependent on the density of defects, while that due to adatom defects is independent of the density of defects. It reduces to zero with decrease in the density of substitutional atoms. However, it increases with decrease in density of vacancies. The graphene sheet with B adatoms is nonmagnetic, but with C and N adatoms it is magnetic. The adatom defects distort the graphene sheet near the defect perpendicular to the sheet. The distortion in graphene due to C and N adatoms is significant, while the distortion due to B adatoms is very small. The vacancy and substitutional atom (B, N) defects in graphene are planar in the sense that there is in-plane displacement of C atoms near the vacancy and substitutional defects. Upon relaxation the displacement of C atoms and the formation of pentagons near the vacancy site due to Jahn–Teller distortion depends upon the density and packing geometry of vacancies.

We have calculated the magneto-optical (MO) properties of Co₂FeX (X =  Al, Ga, Si and Ge) Heusler compounds using the full potential linearized augmented plane wave (FPLAPW) method as implemented in the WIEN2K code using the local spin density approximation (LSDA) and also by using the generalized gradient approximation (GGA) for the electronic exchange and correlation. In all the compounds, Kerr rotation θ_K has a strong minimum near 2 eV, the value of |θ_K| corresponding to this minimum being almost as large as in pure Co–Fe compounds. The calculated MO spectra help to identify the features of the experimental spectra. A comparison of the results shows that the Kerr spectrum is quite similar from both LSDA and GGA but the latter gives better agreement with experiment. Moreover, we find that inclusion of correlation effects using GGA+U removes the discrepancy in magnetic moment of Co₂FeX (X =  Si, Ge) though it has an insignificant effect on the Kerr spectra.

In this study, the transport and magnetic properties of electron-doped perovskites R_xCa_1−xMnO₃ (R = La, Y and Ce) were investigated. As the R ion content increases, the crystal structure, resistivity, magnetoresistance, magnetization and related characteristic temperature of these systems all vary systematically. The data show that the variations in the electrical transport properties are mainly dependent on carrier concentration, whereas the magnetic properties of these systems are also dependent on crystal structure. When the carrier concentration exceeds a certain level, charge ordering occurs, leading to the localized electronic state and peaks in the magnetization curves. The magnetic transition temperature T_N can be well described by crystal structural parameters, suggesting that crystal structure and magnetic properties are strongly coupled to each other.

We report three prominent observations made on the nanoscale charge ordered (CO) manganites RE_1−xAE_xMnO₃ (RE = Nd,Pr; AE = Ca; x = 0.5) probed by temperature dependent magnetization and magneto-transport, coupled with electron magnetic/paramagnetic resonance spectroscopy (EMR/EPR). First, evidence is presented to show that the predominant ground state magnetic phase in nanoscale CO manganites is ferromagnetic and it coexists with a residual anti-ferromagnetic phase. Secondly, the shallow minimum in the temperature dependence of the EPR linewidth shows the presence of a charge ordered phase in nanoscale manganites which was shown to be absent from the DC static magnetization and transport measurements. Thirdly, the EPR linewidth, reflective of spin dynamics, increases significantly with a decrease of particle size in CO manganites. We discuss the interesting observations made on various samples of different particle sizes and give possible explanations. We have shown that EMR spectroscopy is a highly useful technique to probe the 'hindered charge ordered phase' in nanoscale CO manganites, which is not possible by static DC magnetization and transport measurements.

Jiang et al (2004 J. Phys.: Condens. Matter16 521) present a model based on the traditional broken-bond model for predicting surface energies of elemental crystals. It is found that bias errors can be produced in calculating the coordination numbers of surface atoms, especially in the prediction of high-Miller-index surface energies.

In reply to the comment by Luo et al, our theoretical model for the surface energy of elemental crystals is further developed to improve the prediction accuracy of the surface energy of the high-Miller-index facets. It is considered that the previous predicted unit surface area could not denote the actual one since the facets now are uneven. With the modification, the accuracy for the prediction of surface energy in units of J m⁻² is improved.

It has come to the attention of the author that in the above article a number of errors occurred.

• There is a mistake in the first paragraph on page 4. It should read eβψ < 1 instead of eψ < 1, so that it is dimensionless.

• On page 4, in section 2.2.1, both occurrences of reference [17] should read [12,13].

• Further to this the following references are corrected as [116] Cherstvy A G and Winkler R G 2006 J. Chem. Phys.125 064904 [117] Winkler R G and Cherstvy A G 2007 J. Phys. Chem. B 111 8486–93 [164] Assoud L, Messina R and Löwen H 2007 Europhys. Lett.80 48001