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Droplets and bubbles are thought to be two sides of the same coin; this work determines how true this is at the molecular scale. Stable cylindrical nanodroplets and nanobubbles are obtained in Molecular Dynamics (MD) simulations with three-phase contact lines pinned by alternate hydrophobic and hydrophilic patterns. The surface tension and Tolman length for both types of curved interfaces are obtained with the Kirkwood–Buff method, based on the difference between normal and tangential pressure components. Both bubble and droplet cases are compared to the flat interface case for reference. Results show that the surface tension decreases linearly while the Tolman length increases linearly with the gas/liquid density ratio. By running a careful parameter study of the flat interface over a range of densities, the effect of the density ratio can be corrected isolating the effects of curvature on the surface tension and Tolman length. It is found that such effects start to be seen when the equimolar curvature radius goes down to 20 reduced Lennard–Jones (LJ) units. They have the same magnitude but act with opposite signs for nanodroplet and nanobubble interfaces. Considering effects of the density ratio and curvature, a fitted Tolman equation was obtained, which predicts the surface tension of a curved interface. Results obtained by the fitted Tolman equation agree well with those obtained by the MD simulations except at very small curvature radius (

A new method to determine the arbitrary electron energy distribution function (EEDF) from the optical emission spectroscopic measurement in atmospheric-pressure plasma is introduced. The optical emission spectroscopy (OES) continuum emission spectrum, dominated by electron-neutral bremsstrahlung radiation, is analyzed to inspect the usefulness of the conventional OES measurement range for EEDF determination. The EEDF is reconstructed from the OES continuum radiation spectrum by applying machine learning to solve the bremsstrahlung emissivity equation inversely. Through iterative statistical analysis, the presented genetic algorithm can locate the EEDF reliably. Verification of the algorithm shows that theoretical Maxwellian and Druyvesteynian EEDFs can be partially reconstructed from a realistic OES measurement range. Furthermore, preliminary experimental EEDF results of an argon dielectric barrier discharge (DBD) OES measurement are given. The electron energy range and resolution of the determined EEDF are discussed. The results in this paper show potential for accurate determination of the arbitrary EEDF in atmospheric-pressure plasma using simple OES equipment.

We have employed a variable stripe length method in order to measure the optical gain of GaAs/AlGaAs quantum rings. Although the large lateral diameter of quantum rings ( ∼ 50 nm) with a few nm size distribution is expected to cause a small spectral inhomogeneity ( ∼ 1 %), a broad gain width ( ∼ 300 meV) was observed. This result was attributed to a variation of the vertical heights and variations in localized states that exhibit crescent shaped wavefunctions, whereby the energy levels are distributed over a broad spectral range. When the excitation intensity is decreased, irregular peaks appear in the gain spectrum gradually. Similar phenomena were also observed as the temperature increased. We conclude that excited carriers in quantum rings are distributed stochastically at various localized states and that the population inversion is sensitive to both excitation intensity and temperature.

Mass transport of the Knudsen gas in a porous medium is investigated on the basis of the kinetic theory of gases. First, the mass flow conductance is computed numerically for various porosities and solid grain sizes by stochastic particle simulations (SPS). Then, a kinetic model with a homogeneous scatterer is introduced, which contains the reference Knudsen number as the sole parameter that characterizes the collision frequency of gas molecules with the micro-structural solid surface. With the aid of the standard asymptotic analyses for small and large Knudsen numbers combined with the percolation theory, the effective reference Knudsen number is identified to reproduce the SPS results for a wide range of porosities., This paper is part of the Special Topic, Advances in Micro/Nano Fluid Flows: In Memory of Prof. Jason Reese.

The AC magnetic susceptibility (ACS) of Fe3O4 nanoparticles was measured between 10 kHz and 4 MHz at different temperatures and in applied DC fields. In this frequency range, magnetostatic interactions impact magnetization dynamics even for dilute assemblies. The ACS spectrum of relaxation frequencies changes both with temperature and the addition of a small DC field. Because both the relaxation peak frequency and amplitude can be tuned with the DC field, these results could be applied to magnetic hyperthermia applications to optimize heat delivery.

The stability of liquid films on surfaces are critically important in microscale patterning and the semiconductor industry. If the film is sufficiently thin it may spontaneously dewet from the surface. The timescale and rate of dewetting depend on the film repellency of the surface and the properties of the liquid. Therefore, control over the repellency requires modifying surface chemistry and liquid properties to obtain the desired rate of film retraction. Here, we report how the dynamics of a receding thin liquid stripe to a spherical cap droplet can be controlled by programming surface repellency through a non-contact electrostatic method. We observe excellent agreement between the expected scaling of the dynamics for a wide range of voltage-selected final contact angles. Our results provide a method of controlling the dynamics of dewetting with high precision and locality relevant to printing and directed templating.

We measured current–voltage and optical emission for self-sustained discharges obtained using two forms of cylindrical wire grid cathodes, having either an enclosed or an open end. Enclosure of the open end extended the low-pressure range for a “cathode-confined” or CC mode, from around 12.5 Pa to below 3.5 Pa, conditions at which a “beam” mode discharge otherwise occurs. The modification also caused a dark space to envelop the glow within the cathode, bridged by a bright emission resembling plume for the CC mode, and an electron beam for the beam mode. We explain these results by treating the CC mode as a hollow cathode discharge, for which only γ-electrons that suffer inelastic loss before escaping the cathode grid are significant. For the two cathodes, respective degrees of electron confinement possible for the different sheath configurations predict the low-pressure ranges, and the calculated values of cathode fall for self-sustenance by the hollow cathode effect agree approximately with the experimental voltages across a range of pressures. Plume- and beam-like forms of emission indicate inherently different electron energies, consistent with bulk transport across potential distributions characteristic to the mode. Where these features bridge the enclosed cathode boundary, this shows existence of an otherwise closed potential surface within the cathode, confirmed by the geometry of the plume-CC mode configuration, where the relationship between the main glow and plume interface surfaces indicates the arrangement to self-organize in a state of non-ambipolar current flow. Similarities in the mode structure reported elsewhere for related discharges indicates the findings to be relevant for these also.

The Mn3Ga Heusler alloy possesses different crystalline structures representing a range of properties of interest for spintronic applications. We report on the structural and magnetic characterization of the disordered cubic-fcc L21-Mn2.6Ga thin films grown on MgO(001) substrates. The first two nanometers of thickness of the Mn2.6Ga thin films are highly strained to the substrate with a lattice mismatch of 9.54%, playing the role of a template layer for the subsequent growth of relaxed L21-Mn2.6Ga. Once the films reach a critical thickness of 15 nm, the cubic phase reorients its epitaxial relationship from a (001) to a (111) in-plane orientation. Magnetic measurements show that the samples exhibit perpendicular magnetic anisotropy and also that the usually antiferromagnetic L21-Mn3Ga films are ferromagnetic with a Curie temperature > 400 K due to partially compensated Mn moments.

Extended-magnetohydrodynamics (MHD) transports magnetic flux and electron energy in high-energy-density experiments, but individual transport effects remain unobserved experimentally. Two factors are responsible in defining the transport: electron temperature and electron current. Each electron energy transport term has a direct analog in magnetic flux transport. To measure the thermally driven transport of magnetic flux and electron energy, a simple experimental configuration is explored computationally using a laser-heated pre-magnetized under-dense plasma. Changes to the laser heating profile precipitate clear diagnostic signatures from the Nernst, cross-gradient-Nernst, anisotropic conduction, and Righi-Leduc heat-flow. With a wide operating parameter range, this configuration can be used in both small and large scale facilities to benchmark MHD and kinetic transport in collisional/semi-collisional, local/non-local, and magnetized/unmagnetized regimes.

Strongly confined fluids exhibit inhomogeneous properties due to atomistic structuring in close proximity to a solid surface. State variables and transport coefficients at a solid-fluid interface vary locally and become dependent on the properties of the confining walls. However, the precise mechanisms for these effects are not known as of yet. Here, we make use of nonequilibrium molecular dynamics simulations to scrutinize the local fluid properties at the solid-fluid interface for a range of surface conditions and temperatures. We also derive microscopic relations connecting fluid viscosity and density profiles for dense fluids. Moreover, we propose empirical ready-to-use relations to express the average density and viscosity in the channel as a function of temperature, wall interaction strength, and bulk density or viscosity. Such relations are key to technological applications such as micro-/nanofluidics and tribology but also natural phenomena.

Two custom-made In0.5Ga0.5P p+-i-n+ circular mesa spectroscopic X-ray photodiodes with different diameters (200 μm and 400 μm) and a 5 μm i layer have been characterized for their response to X-ray photons within the energy range 4.95 keV to 21.17 keV. The photodiodes, operating uncooled at 30 °C, were coupled, in turn, to the same custom-made charge-sensitive preamplifier. X-ray fluorescence spectra of high-purity calibration foils excited by a Mo target X-ray tube were accumulated. The energy resolution (Full Width at Half Maximum) increased from 0.79 keV ± 0.02 keV at 4.95 keV to 0.83 keV ± 0.02 keV at 21.17 keV, and from 1.12 keV ± 0.02 keV at 4.95 keV to 1.15 keV ± 0.02 keV at 21.17 keV, when using the 200 μm and 400 μm diameter devices, respectively. Energy resolution broadening with increasing energy was attributed to increasing Fano noise (negligible incomplete charge collection noise was suggested); for the first time the Fano factor for In0.5Ga0.5P was experimentally determined to be 0.13, suggesting a Fano limited energy resolution of 145 eV at 5.9 keV. The charge output of each system had a linear relationship with photon energy, across the investigated energy range. The count rate of both spectroscopic systems increased linearly with varying X-ray tube current up to ~105 photons s-1 cm-2 incident photon fluences. The development of In0.5Ga0.5P based spectrometers is particularly important for hard X-/γ-ray astronomy, due to the material’s large linear X-ray and γ-ray absorption coefficients and ability to operate uncooled at high temperatures.

Propagation properties of an optical vortex with a helical wavefront in cold uniform magnetized plasma are theoretically investigated in an electron cyclotron range of frequencies. The effects of the helical wavefront of the optical vortex on the wave fields in magnetized plasma are described. These effects become significant as the topological charge of the optical vortex increases or the distance from the phase singularity point becomes small. The different properties of propagation are also confirmed in propagation of Laguerre–Gaussian beams by three-dimensional simulations with the finite element method.

Long range corrections (lrc) for the potential energy and for the force in planar liquid-vapor interface simulations are considered for spherically symmetric interactions. First, it is stated that for the Lennard-Jones (LJ) fluid the lrc for the energy Δu of Janecek [J. Phys. Chem. B 110, 6264 (2006)] is the same as that of Lotfi et al. [Mol. Simul. 5, 233 (1990)]. Second, we present the lrc for the force ΔF for any spherically symmetric interaction as a derivative of Δu plus a surface integral over the cut-off sphere by using the extended Leibniz rule of Flanders [Am. Math. Monthly 80, 615 (1973)]. This ΔF corrects the incomplete lrc Δ1F of Lotfi et al. and agrees with the result of Janecek obtained by direct averaging of the forces. Third, we show that the molecular dynamics (MD) results for the surface tension γ of the LJ fluid with size parameter σ obtained by Werth et al. [Physica A 392, 2359 (2013)] with the lrc ΔF of Janecek and a cut-off radius rc = 3σ agree with the results of Mecke et al. [J. Chem. Phys. 107, 9264 (1997)] obtained with the lrc Δ1F of Lotfi et al. and rc = 6.5σ within −0.4% to +1.6%. Moreover, using only the MD results for γ of Werth et al., we obtain for the LJ fluid a new surface tension correlation which also represents the γ-values of Mecke et al. within ±0.7%. The critical temperature resulting from the correlation is Tc = 1.317 66 and is in very good agreement with Tc,ref = 1.32 of the reference equation of state for the LJ fluid given by Thol et al. [J. Phys. Chem. Ref. Data 45, 023101 (2016)].

CR-39 nuclear track material is frequently used for the detection of protons accelerated in laser-plasma interactions. The measurement of track densities allows for determination of particle angular distributions, and information on the kinetic energy can be obtained by the use of passive absorbers. We present a precise method of measuring spectral distributions of laser-accelerated protons in a single etching and analysis process. We make use of a one-to-one relation between proton energy and track size and present a precise calibration based on monoenergetic particle beams. While this relation is limited to proton energies below 1 MeV, we show that the range of spectral measurements can be significantly extended by simultaneous use of absorbers of suitable thicknesses. Examples from laser-plasma interactions are presented, and quantitative results on proton energies and particle numbers are compared to those obtained from a time-of-flight detector. The spectrum end points of continuous energy distributions have been determined with both detector types and coincide within 50-100 keV., This project has been funded by the Spanish Ministry for Economy and Competitiveness within the Retos-Colaboracion 2015 initiative, Ref. No. RTC-2015-3278-1. P. Mur has been awarded a Garantía Juvenil grant.

A new compact gamma-ray spectrometer was developed in order to optimise the measurement of bremsstrahlung radiation emitted from runaway electrons in the MeV range. The detector is based on a cerium doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator coupled to a silicon photomultiplier and is insensitive to magnetic fields. A dedicated electronic board was developed to optimise the signal readout as well as for online control of the device. The detector combines a dynamic range up to 10 MeV with moderate energy non-linearity, counting rate capabilities in excess of 1 MHz, and an energy resolution that extrapolates to a few % in the MeV range, thus meeting the requirements for its application to runaway electron studies by bremsstrahlung measurements in the gamma-ray energy range.

In November 2012, the peculiar TeV emitting active galactic nucleus of IC 310 showed an impressively bright gamma-ray flare on variability time scales of minutes. The shock-in-jet model fails to explain the photon flux flickering and the hard energy spectrum, if the source has a viewing angle of 10-20 degrees as radio observations suggest. Preferably, a magnetospheric model for the acceleration of particles and gamma-ray emission is proposed. An extensive multi-wavelength campaign in November 2012 until January 2013 was conducted including instruments from the radio up to the very-high-energy range. Here, we present the status of the results of this campaign and an interpretation consistent with an afterglow from the black hole lightning, with which we associated the 2012 event.

Spectral analysis of optically excited currents in single-crystal (100)InAs/amorphous (a-)Al2O3/ metal structures allows one to separate contributions stemming from the internal photoemission (IPE) of electrons into alumina and from the trapping-related displacement currents. IPE spectra suggest that the out-diffusion of In and, possibly, its incorporation in a-Al2O3 lead to the development of 0.4 eV wide conduction band (CB) tail states. The top of the InAs valence band is found at 3.4560.10 eV below the alumina CB bottom, i.e., at the same energy as at the GaAs/a-Al2O3 interface. This corresponds to the CB and the valence band offsets at the InAs/a-Al2O3 interface of 3.160.1 eV and 2.560.1 eV, respectively. However, atomic-layer deposition of alumina on InAs results in additional low-energy electron transitions with spectral thresholds in the range of 2.0–2.2 eV, which is close to the bandgap of AlAs. The latter suggests the interaction of As with Al, leading to an interlayer containing Al-As bonds providing a lower barrier for electron injection. received: 2016-09-05 accepted: 2016-11-17 published: 2016-12-15 ispartof: Journal of Applied Physics vol:120 issue:23 pages:235701-1 status: published

The movement of particles in the range from 0.5 to 500 μm in mass median diameter on a two-dimensional vibrating plate is observed through a high-speed digital camera with a zoom lens. The results show that larger particles saltate higher, while smaller particles easily agglomerate and slightly saltate because of the low restitution of their loosely packed structure. The salation heights are in good agreement with the results calculated by a model based on gravity, adhesion, drag force, and restitution., "Powders and Grains 2013"; Conference date: 8–12 July 2013; Location: Sydney, Australia

Relaxation times and transport processes of many glass-forming supercooled liquids exhibit a super-Arrhenius temperature dependence. We examine this phenomenon by computer simulation of the Lewis-Wahnström model for ortho-terphenyl. We propose a microscopic definition for a single-molecule cage-breaking transition and show that, when correlation behaviour is taken into account, these rearrangements are sufficient to reproduce the correct translational diffusion constants over an intermediate temperature range in the supercooled regime. We show that super-Arrhenius behaviour can be attributed to increasing negative correlation in particle movement at lower temperatures and relate this to the cage-breaking description. Finally, we sample the potential energy landscape of the model and show that it displays hierarchical ordering. Substructures in the landscape, which may correspond to metabasins, have boundaries defined by cage-breaking transitions. The cage-breaking formulation provides a direct link between the potential energy landscape and macroscopic diffusion behaviour.

We report an experimental and theoretical study of the collapse time of a gas bubble injected into an otherwise stagnant liquid under quasi-static conditions and for a wide range of liquid viscosities. The experiments were performed by injecting a constant flow rate of air through a needle with inner radius a into several water/glycerine mixtures, providing a viscosity range of 20 cP ≲ μ ≲ 1500 cP. By analyzing the temporal evolution of the neck radius, R0(t), the collapse time has been extracted for three different stages during the collapse process, namely, Ri/a = 0.6, 0.4, and 0.2, being Ri = R0(t = 0) the initial neck radius. The collapse time is shown to monotonically increase with both Ri/a and with the Ohnesorge number, Oh=μ/ρσRi, where ρ and σ represent the liquid density and the surface tension coefficient, respectively. The theoretical approach is based on the cylindrical Rayleigh-Plesset equation for the radial liquid flow around the neck, which is the appropriate leading-order representation o...

We have measured multipoint fluctuations inside a divertor simulation experimental module (D-module) during the transient discharge from attached to detached states in the tandem mirror device GAMMA 10/PDX. It was first observed that blob-/hole- like positive/negative spikes of the ion saturation current appeared non-periodically around the radially outer side edge on the V-shaped target plate. This tendency became outstanding in the transient state, and the typical speed and size of the isolated blob-like structures in the azimuthal direction were estimated. Additionally, lower-frequency periodic mode fluctuations and their changes due to plasma detachment were investigated not only in the D-module but also in the central cell with the microwave interferometer, etc. Odd and even modes continuously appeared during the discharge, in the range of several kilohertz., ファイル公開：2019/08/01

We investigate carrier transport properties of silicon nanowire (SiNW) arrays decorated with TiO2 nanoparticles (NPs). Ohmic conduction was dominant at lower voltages and space charge limited current with and without traps was observed at higher voltages. Mott's 3D variable range hoping mechanism was found to be dominant at lower temperatures. The minimum hopping distance (Rmin) for n and p-SiNWs/TiO2 NPs devices was 1.5 nm and 0.68 nm, respectively, at 77 K. The decrease in the value of Rmin can be attributed to higher carrier mobility in p-SiNWs/TiO2 NPs than that of n-SiNWs/TiO2 NPs hybrid device.

Gamma Ray Bursts (GRBs) are immensely energetic explosions radiating up to 10^54 erg of energy isotropically (Eiso) and they are observed within a wide range of redshift (from ̃ 0.01 up to ̃ 9). Such enormous power and high redshift point at these phenomena being highly favorable to investigate the history and evolution of our universe. The major obstacle in their application as cosmological study-tools is to find a way to standardize the GRBs, for instance similar to SNe Ia. With respect to this goal, the correlation between spectral peak energy (Ep,i) and the "intensity" is a positively useful and investigated criterion. Moreover, it has been demonstrated that, through the Ep,i - Eiso correlation, the current data set of GRBs can already contribute to the independent evidence of the matter density Ω_M being ̃ 0.3 for a flat universe scenario. We try to inspect and compare the correlations of Ep,i with different intensity indicators (e.g., radiated energy, average and peak luminosity, bolometric vs. monochromatic quantities, etc.) both in terms of intrinsic dispersion and precise estimation of Ω_M. The outcome of such studies are further analyzed in verifying the reliability of the correlations for both GRB physics and their standardization for cosmology.

The multicanonical Monte Carlo method is applied to a bulk Lennard-Jones fluid system to investigate the liquid-solid phase transition. We take the example of a system of 108 argon particles. The multicanonical weight factor we determined turned out to be reliable for the energy range between -7.0 and -4.0 kJ/mol, which corresponds to the temperature range between 60 and 250 K. The expectation values of the thermodynamic quantities obtained from the multicanonical production run by the reweighting techniques exhibit the characteristics of first-order phase transitions between liquid and solid states around 150 K. The present study reveals that the multicanonical algorithm is particularly suitable for analyzing the transition state of the first-order phase transition in detail.

Estimates of particle size distributions (PSDs) in solid-in-liquid suspensions can be obtained from measurements of ultrasonic wave attenuation. The technique is based on adaptively fitting theoretical wave propagation models to the measured data across a frequency range. These models break down at high solid concentrations and it is believed that this failure is due to the effective viscosity of the mixture in the vicinity of the particles being different from that of the continuous phase. This paper discusses PSD estimation when a number of different viscosity formulations are incorporated into the wave propagation model. The viscosity model due to Happel provides the best estimate of PSD in suspensions of medium concentration.

A magnetoelectric (ME) sensor exhibiting wideband behavior as a function of applied magnetic DC bias and frequency was designed by combining the dimensionally gradient piezoelectric layer with Metglas magnetostrictive layers in laminate configuration. The ME coefficient of the band in the DC magnetic range of 52-242 Oe was measured to be 3000 mV/cm Oe under the resonant condition of f = 107 kHz. The wideband in the AC magnetic field frequency range of 41-110 kHz had the ME coefficient in the vicinity of 260 mV/cm Oe under the conditions of H-AC = 1 Oe and H-DC = 70 Oe. This frequency-dependent ME behavior clearly showed two different states on each side of the resonance peak which could open the possibility of developing new applications such as magnetic field-controlled switches. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4720095] Office of Basic Energy Science, Department of Energy, USA DE-FG02-08ER46484

We have calculated the interfacial properties of fully flexible chains formed from tangentially bonded Lennard-Jones beads by direct coexistence. The full long-range tails of the potential are accounted for by means of inhomogeneous long-range corrections consisting in slice by slice summation of interactions away from the truncation sphere. We show that the corrections may be transformed into an effective long-range pair potential plus a self term, thus allowing for a fast and easy implementation of the method. After addition of the effective pair potential, the coexistence densities agree very well with results from Gibbs-ensemble simulations with usual homogeneous long-range corrections. We calculate the surface tensions without the need for explicit evaluation of the virial by using the wandering interface and test area methods. Comparison with surface tensions obtained previously for chains of truncated Lennard-Jones beads show a very large contribution of interactions beyond truncation radii as large as four bead diameters. The percentage change is about 40% for low temperatures but may increase beyond 60% for high temperatures, thus revealing the need for proper account of long-range corrections for models with untruncated interactions. The study of interfacial properties with chain length shows asymptotic increase for the surface tension and related asymptotic decrease for the interfacial width., We wish to acknowledge helpful discussions with E. de Miguel, G. Jackson, and C. Vega and P. Bryk. This work was supported by Ministerio de Educación y Ciencia through Grant Nos. FIS2007-66079-C02-01 and FIS2007-66079- C02-02. Further financial support from projects PR34/07- 15906 (Santander-UCM), CCG08-UCM/ESP-4358 (CAM– UCM), MOSSNOHO-S0505/ESP/0299 (CAM), and P07- FQM02884 (Junta de Andalucía) is also acknowledged. One of us (F.J.B.) also thanks Universidad de Huelva for additional support.

Arrays of tunnel magnetoresistance sensors based on MgO as insulating layer are employed to detect magnetic microbeads. For single bead detection, elliptically shaped sensors of axis lengths of 400 and 100 nm are used. Due to high shape anisotropy a linear response of the sensor signal in a magnetic field range between −500 and 500 Oe can be reported. By performing static detection measurements of magnetic microbeads, a distinct signal shape correlated with the position of beads in respect to the sensor can be observed. The experimental data are compared to micromagnetic simulations carried out on a trilayer model.

This work reports on the quantification of self-sputtering and implantation occurring during pulsed laser deposition of Au as a function of the laser fluence used to ablate the gold target. The experimental approach includes, on one hand, in situ electrical (Langmuir) and optical (two-dimensional imaging) probes for determining, respectively, ion and excited neutral kinetic energy distributions. On the other hand, it includes determination of the density of (i) ions reaching a substrate, and (ii) gold atoms deposited on a substrate as well as of a proportion of atoms that are self-sputtered. The experimental results supported by numerical analysis show that self-sputtering and implantation are both dominated by ions having kinetic energies ≥200 eV. They are a fraction 0.60-0.75 of the species arriving to the substrate for ablation laser fluences 2.7-9.0 J cm-2. Self-sputtering yields in the range 0.60-0.86 are determined for the same fluence range. © 2008 American Institute of Physics., This work was partially supported by Project No. MAT2005-06508-C02-01 of MEC Spain and by Project No. HPRN-CT-2002-00328 of EU.

We present a detailed computer simulation study of the phase behavior of the Gay–Berne liquid crystal model with molecular anisotropy parameter k=4.4. According to previous investigations: (i) this model exhibits isotropic (I), smectic-A (Sm-A), and smectic-B (Sm-B) phases at low pressures, with an additional nematic (N) phase between the I and Sm-A phases at sufficiently high pressures; (ii) the range of stability of the Sm-A phase turns out to be essentially constant when varying the pressure, whereas other investigations seem to suggest a pressure-dependent Sm-A range; and (iii) the range of stability of the Sm-B phase remains unknown, as its stability with respect to the crystal phase has not been previously considered. The results reported here do show that the Sm-A phase is stable over a limited pressure range, and so it does not extend to arbitrarily low or high pressures. This is in keeping with previous investigations of the effect of molecular elongation on the phase behavior of Gay–Berne models. A detailed study of the melting transition at various pressures shows that the low-temperature crystalline phase melts into an isotropic liquid at very low pressures, and into a nematic liquid at very high pressures. At intermediate pressures, the crystal melts into a Sm-A liquid and no intermediate Sm-B phase is observed. On the basis of this and previous investigations, the reported Sm-B phase for Gay–Berne models appears to be a molecular solid rather than a smectic liquid phase., Financial support of the Spanish DGICYT (Dirección General de Investigación Científica y Técnica) under Project No. BFM-2001-1420-C02-02 is acknowledged. Additional support from Universidad de Huelva and Junta de Andalucía is also acknowledged.