Born Mayer Huggins Potential Research Articles

Pairon Green’s function for high-Tc superconductors

Considering the many-body quantum dynamics, the pairon Green’s function has been developed via a Hamiltonian that encompasses the contribution of pairons, pairon-phonon interactions, anharmonicities, and defects. To obtain the renormalized pairon energy dispersion, the most relevant Born–Mayer–Huggins potential has been taken into account. The Fermi surface for the representative [Formula: see text] high-[Formula: see text] superconductor has been obtained via renormalized pairon energy relation. This revealed the [Formula: see text]-shape superconducting gap with a nodal point along [Formula: see text] direction. Further, the superconducting gap equation has been derived using the pairon density of states. The developed gap equation is the function of temperature, Fermi energy, and renormalized pairon energy. The temperature variation of the gap equation is found to be in good agreement with the BCS gap equation. Also, this reveals the reduced gap ratio ([Formula: see text] for [Formula: see text]) in the limit (5–8) of the reduced gap ratio designated for high-[Formula: see text] superconductors.

Thermodynamics and structural properties of CaO: A molecular dynamics simulation study.

A detailed theoretical study of CaO in the solid and liquid states by means of combined classical and ab initio molecular dynamics simulations is presented. Evolution of the specific heat capacity at constant pressure as a function of temperature is studied, and the melting temperature and enthalpy of fusion are determined. It is shown that an empirical Born-Mayer-Huggins potential gives a good representation of pure CaO in the liquid and solid states as compared to available experimental data and density functional theory calculations. Consistency of the predicted results obtained for CaO with the data available in commercial thermodynamic databases and experimental values in the literature is discussed. The present methodology and theoretical results provide a new accurate basis for calculations of thermodynamic properties in a temperature range that is hardly accessible by experiments.

Pairing Symmetry, Nodal and Antinodal Superconducting Gap in $$\text {La}_{2-x}\text {Sr}_x\text {CuO}_{4}$$: A Doping Scenario

Using the many-body quantum dynamics and Dyson’s equation formalism, the phonon Green’s function has been developed via a Hamiltonian that includes the contribution of harmonic electron and phonon field and their interaction, phonon field anharmonicities and defects. The renormalized electron–phonon dispersion is obtained using the modified form of Born–Mayer–Huggins potential (MBMHP) and phonon Green’s function for a representative high-temperature superconductor (HTS) $$\text {La}_{2-x}\text {Sr}_x\text {CuO}_4$$. The in-plane gap analysis has produced a v-shaped gap that confesses the anisotropy of the superconducting gap (SG). The nodal gap, antinodal gap and SG exhibit increment with decreasing doping with the vanishing of the nodal gap at $$x=0.104$$. A dominated $$d_{x^2-y^2}$$ pairing symmetry is observed along with a small component of s or $$d_{xy}$$ pairing state in the underdoped regime. The variation in the nodal gap, antinodal gap and SG shows monotonic increment with decreasing doping. It is found that doping has a nonlinear effect on $$d_{x^2-y^2}$$ pairing symmetry. The impact of antiferromagnetic (AF) spin fluctuations has been incorporated in the SG equation and on the pairing symmetry.

Simulation of structural characteristics of Mullite melt at high pressure

Molecular dynamics (MD) simulation is applied to investigate the structural characteristics of Al2O3–SiO2 system with the Al2O3 content at 60 mol.% (Mullite — 3Al2O[Formula: see text]2SiO2). MD models containing 5250 atoms in cubic box with periodic boundary conditions are constructed at 3500 K in 0–100 GPa pressure range. The Born–Mayer–Huggins potential is applied in this study. Based on the cluster analyzes and MD data visualization technique, the structural characteristics of Mullite melt, such as the short-range and intermediate-range order, the local environments of oxygen and network structure will be clarified. Under compression, the Al–O bonds are broken, leading to incorporation of Al atoms into Si–O subnet through both nonbridging oxygen (NBO) and bridging oxygen (BO), forming –Al–O–Si-network (Al–O–Si, Si–O–Al2, Si2–O–Al, Si–O–Al3, Si2–O–Al2 and Si3–O–Al). The degree of polymerization (DOP) of the silica network and alumina network increase with pressure and the DOP of SiOx-network is lower than that of AlO[Formula: see text]-network under compression. The statistics of corner, edge and face-sharing bonds between two adjacent TO[Formula: see text] units (T is Si, Al; x = 3–7) as well as characteristics of all type OT[Formula: see text] linkages (y = 2–6) are investigated in detail. Structural and compositional heterogeneities are clarified via analysis of structure and size distribution of TO[Formula: see text]-clusters.

Impurity induced renormalized phonon spectrum of cuprate superconductors

The potential problem of anharmonic lattice vibrations in high-temperature superconductors (HTS) using the most suitable Born–Mayer–Huggins (BMH) potential has been taken up to investigate the renormalized phonon density of states (RPDOS). In order to develop the suitable results, the many body theory using quantum dynamical approach of Green’s function (GF) via an almost complete Hamiltonian (without using BCS type Hamiltonian) has been incorporated which includes harmonic electron and phonon Hamiltonian, electron–phonon interaction Hamiltonian, anharmonic and defect Hamiltonian. The derivation of anharmonic phonon GF for modified form of BMH potential enables to evaluate the renormalized and perturbed mode phonon frequencies of solids. The expressions obtained for the RPDOS can be resolved into diagonal and nondiagonal parts of which the nondiagonal part chiefly depends on impurities and disappears in pure crystals. A large number of new features are investigated in the light of this formulation followed by the numerical analysis for the energy spectrum of representative cuprate HTS YBa2Cu3O[Formula: see text]. The inclusion of defects, anharmonicities and electron–phonon interactions in the cuprate superconductors substantially modifies the scenario of RPDOS and reveals a large number of unexplained peaks in the spectrum.

Investigation of the local structures and transport properties of quaternary molten alkali chloride systems by MD simulations for liquid metal batteries

When selecting a suitable molten salt electrolyte system for liquid metal batteries (LMBs), it is crucial to have an accurate understanding of the local structures and transport properties of molten salt mixtures. In this study, molecular dynamics simulations have been employed to calculate such properties of (Li, Na, K, Cs)Cl and (Li, K, Rb, Cs)Cl quaternary molten alkali chloride systems at 700–1000 K using the Born–Mayer–Huggins potential. The results show that the density and shear viscosity of the molten salt electrolyte increase when the average cation radius increases, while the self-diffusion coefficient and ionic conductivity decrease. Increasing the temperature in LMBs can enhance the diffusibility and electroconductivity of the molten salt electrolyte and reduce the density and shear viscosity to a certain extent. Overall, the calculated results provide a useful reference for the selection of molten salt electrolytes with reasonable composition to optimize the electrochemical performance of LMBs. The molten salt mixtures as the electrolytes have a crucial effect on the performances of LMBs. The transport properties such as ionic conductivity, shear viscosity and self-diffusion capacity of quaternary molten salt systems (Li, Na, K, Cs)Cl and (Li, K, Rb, Cs)Cl have been calculated by MD simulation, and the simulation results can provide guidance for the researches of LMBs in the future.

Superconducting gap anisotropy and d-wave pairing in YBa2Cu3O7−δ

Considering Born–Mayer–Huggins potential as a most suitable potential to study the dynamical properties of high-temperature superconductors (HTS), the many-body quantum dynamics to obtain phonon Green’s functions has been developed via a Hamiltonian that incorporates the contributions of harmonic electron and phonon fields, phonon field anharmonicities, defects and electron–phonon interactions without considering BCS structure. This enables one to develop the quasiparticle renormalized frequency dispersion in the representative high-temperature cuprate superconductor YBa2Cu3O[Formula: see text]. The superconducting gap shows substantial changes with increased doping. The in-plane gap study revealed a [Formula: see text]-shape gap with a nodal point along [Formula: see text] direction for optimum doping ([Formula: see text] = 0.16) and the nodal point vanished in underdoped and overdoped regimes. The d[Formula: see text] pairing symmetry is observed at optimum doping with the presence of s or d[Formula: see text] components ([Formula: see text] 3%) in underdoped and overdoped regimes.

Atomistic simulations of nanocrystalline U 0.5 Th 0.5 O 2 solid solution under uniaxial tension

Abstract Molecular dynamics simulations were performed to investigate the uniaxial tensile properties of nanocrystalline U 0.5 Th 0.5 O 2 solid solution with the Born–Mayer–Huggins potential. The results indicated that the elastic modulus increased linearly with the density relative to a single crystal, but decreased with increasing temperature. The simulated nanocrystalline U 0.5 Th 0.5 O 2 exhibited a breakdown in the Hall–Petch relation with mean grain size varying from 3.0 nm to 18.0 nm. Moreover, the elastic modulus of U 1- y Th y O 2 solid solutions with different content of thorium at 300 K was also studied and the results accorded well with the experimental data available in the literature. In addition, the fracture mode of nanocrystalline U 0.5 Th 0.5 O 2 was inclined to be ductile because the fracture behavior was preceded by some moderate amount of plastic deformation, which is different from what has been seen earlier in simulations of pure UO 2 .

Temperature and concentration dependence of the physical properties and local structures of molten NaCl-KCl-LiCl mixtures

Abstract A systematic investigation of a LiCl-NaCl-KCl ternary system was performed by using non-equilibrium molecular dynamic methods. The influence of temperature and LiCl concentration on density; as well as the structures and transport properties of molten salts were investigated. The structures of molten mixtures were studied via an analysis of pair distribution functions and distribution of individual ion coordination numbers. Pair distribution functions suggest that interactions between unlike ions decrease with increases in LiCl content. The coordination number of Li + ion increases as LiCl concentration increasing. An investigation of the diffusion coefficients suggests that the ionic diffusion coefficient increases with increasing LiCl concentration. The calculations also show that the Born–Mayer–Huggins potential together with the non-equilibrium molecular dynamics method predicts positive temperature dependences for self-diffusion coefficients, and negative temperature dependences for viscosity of molten ternary mixtures. The simulation results agree with the experimental data available in the literature and the calculated results regarding mixing behavior follow the mixing rules for an ideal liquid.

The Born–Mayer–Huggins potential in high temperature superconductors

The Born–Mayer–Huggins potential which has been found the best suitable potential to study the YBa2Cu3O[Formula: see text] type high temperature superconductors is revisited in a new framework. A deeper insight in it reveals that the Born–Mayer parameters for different interactions in high temperature superconductor are not simple quantities but several thermodynamic and spatial functions enter the problem. Based on the new theory, the expressions for pressure, bulk modulus and Born–Mayer parameters have been derived and it is established that these quantities depend upon Gruneisen parameter which is the measure of the strength of anharmonic effects in high temperature superconductors. This theory has been applied to a specific model YBa2Cu3O[Formula: see text] crystal for the purpose of numerical estimates to justify the new results.

Molecular dynamics simulation of silver nanoparticles in a europium doped sodosilicate glass

Molecular dynamics simulation is applied to an europium doped sodosilicate glass containing silver [(Na–Ag) 2O–SiO 2–Eu 2O 3]. The silver is implanted in substitution of Na, simulating an ionic exchange. For ionic interactions a modified Born–Mayer–Huggins potential was employed. For the Ag–Ag interaction, a Lennard-Jones (LJ) potential is applied, while for the Eu–Ag interaction, a modified LJ potential is introduced. The particle size increases with the annealing treatment and follows a lognormal law. After 75 ps the average particle size reaches 5.8 atoms (4.8 for Ag and 1.0 for Eu), and it is found that the europium is preferentially situated on these nanoclusters.

Submonolayer growth of BaTiO3 thin film via pulsed laser deposition: A kinetic Monte Carlo simulation

Distinguishing with the traditional solid-on-solid model, the adatom bonding is specially considered to describe the atom combined according to the perovskite structure, and the pulsed laser deposition growth of the perovskite thin film on the surface of square lattice substrate of homoepitaxial system is considered as three stochastic incidents such as the deposition, diffusion, and bonding of adatoms. We proposed an energy-dependent kinetic Monte Carlo approach to simulate BaTiO3 thin film growth via pulsed laser deposition within the submonolayer regime, in which the coverage θ is less than 1. In the simulation, first- and second-nearest-neighbor interactions are taken into account by the Born–Mayer–Huggins potential. Varying the values of the laser repetition rate and pulse duration, the relative curves of the island density and island size versus coverage were obtained. The simulation results show that the island density increases, while the island size decreases with the pulse frequency. When the pulse repetition rate is less than 1 kHz, there is no obvious variation for the curves of the island density and island size versus coverage. However, when the pulse repetition rate is larger than 1 kHz, the island density does not change for θ<0.1, and with the pulse duration, the island density increases while the island size decreases for θ>0.1. They are in good agreement with the previous experimental observations. It provides an understanding of the evolution of the morphology of the BaTiO3 thin film in submonolayer growth and a basic exploration of the epitaxial growth process of ionic oxides with perovskite-type structures.

Kinetic Monte Carlo simulation of RHEED from BaTiO3 thin films

Abstract We proposed an energy-dependent kinetic Monte Carlo approach to simulate the reflection high-energy electron diffraction intensity during the three-dimensional growth of BaTiO3 thin film using pulsed laser deposition. In the simulation, we employed the Born–Mayer–Huggins potential and assumed the overhanging of atoms in the deposition and diffusion process. The factors considered include the incident kinetic energy, laser repetition rate and mean deposition rate. By changing the values relative to every factor, the effects on the reflection high-energy electron diffraction (RHEED) intensity were studied. Being in good agreement with the experimental observations, the results provide an understanding on the evolution of the morphology about BaTiO3 thin film and a basic exploration of the epitaxial growth process of ionic oxides with perovskite-type structures.

Molecular dynamics studies of phase transition of KI clusters

Structural, energetic, and dynamics aspects of phase transitions of several KI clusters have been analyzed by molecular dynamics simulations. Born–Mayer–Huggins potential function was employed to reproduce melting and freezing when clusters are heated and cooled. Various diagnostic methods were applied to molecular dynamics simulations of heating and cooling stages including caloric curves, the Lindemann index, diffusion coefficients, and pair-correlation functions. Results demonstrate clusters of salt behave very differently from clusters of nonpolar molecule and melting temperatures decreased approximately linearly with the reciprocal of cluster radius, as expected according to conventional, attractive Reiss, Mirabel, and Whetten model. The melting temperature of bulk KI obtained by extrapolation is close to the experiment.

Molecular Dynamics Studies of the Kinetics of Phase Changes in Clusters: Crystal Nucleation of (RbCl)108 Clusters at 600, 550, and 500 K

Molecular dynamics computer simulations based on the Born–Mayer–Huggins potential function have been employed to study the crystal nucleation of (RbCl)108 clusters. When a completely melted (RbCl)108 cluster was cooled down at a cooling rate of 2.5×1011 K/s, nucleation and crystal growth into the NaCl-type structure crystal was observed at the temperature ∼600 K. When a melted (RbCl)108 cluster was quenched from 900 K to a bath with a temperature from 600 to 500 K and kept in the bath for a time period up to ∼720 ps, both nucleation and crystal growth into the NaCl-type crystals were observed. Nucleation rates of crystallization at 600, 550, and 500 K are estimated and the interfacial free energy of the liquid–solid boundary was derived from the nucleation rates using the classical nucleation theory. The diffuse interface thickness was also estimated. The possibility of the transition from NaCl-type to CsCl-type structure under high Laplace pressure is discussed.

Molecular dynamics of phase transitions in clusters of alkali halides

Molecular dynamics simulations of unconstrained alkali halide clusters with 8, 64, 216, 512, 1000, 1728, 2744, 4096, 5832, and 8000 ions have been carried out using the Born–Mayer–Huggins potential. All the clusters exhibit first-order melting and freezing transitions. The melting temperature increases with the number of ions and approaches the melting temperature of the bulk. Clusters with a number of ions less than approximately 1000 present hysteresis cycles and practically do not have phase coexistence. Clusters with a number of ions over 1000 present phase coexistence during a significant part of the transition region and hysteresis is progressively eliminated as the clusters size increases. It is suggested that hysteresis is an intrinsic characteristic of small clusters. In the transition regions the calculations have been performed by fixing the total energy of the clusters. It is shown that such a technique provides a better way of analyzing the transition mechanism than the usual procedure of fixing the temperature by ad hoc rescaling the velocities or by using canonical molecular dynamics or Monte Carlo. A detailed analysis of the melting transition is presented. The effects of interfaces and impurities are discussed. A method based on the velocity autocorrelation functions is proposed, in order to determine the molar fraction of the ions present in the solid and liquid phases as well as to produce colored snapshots of the phases in coexistence. The overall agreement of the estimated melting points and enthalpies of melting with the experiment is fairly good. The estimated melting point and enthalpy of melting for KCl in particular are in excellent agreement with the experimental values. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 169–180, 2001

Molecular dynamics of phase transitions in clusters of alkali halides

AbstractMolecular dynamics simulations of unconstrained alkali halide clusters with 8, 64, 216, 512, 1000, 1728, 2744, 4096, 5832, and 8000 ions have been carried out using the Born–Mayer–Huggins potential. All the clusters exhibit first‐order melting and freezing transitions. The melting temperature increases with the number of ions and approaches the melting temperature of the bulk. Clusters with a number of ions less than approximately 1000 present hysteresis cycles and practically do not have phase coexistence. Clusters with a number of ions over 1000 present phase coexistence during a significant part of the transition region and hysteresis is progressively eliminated as the clusters size increases. It is suggested that hysteresis is an intrinsic characteristic of small clusters. In the transition regions the calculations have been performed by fixing the total energy of the clusters. It is shown that such a technique provides a better way of analyzing the transition mechanism than the usual procedure of fixing the temperature by ad hoc rescaling the velocities or by using canonical molecular dynamics or Monte Carlo. A detailed analysis of the melting transition is presented. The effects of interfaces and impurities are discussed. A method based on the velocity autocorrelation functions is proposed, in order to determine the molar fraction of the ions present in the solid and liquid phases as well as to produce colored snapshots of the phases in coexistence. The overall agreement of the estimated melting points and enthalpies of melting with the experiment is fairly good. The estimated melting point and enthalpy of melting for KCl in particular are in excellent agreement with the experimental values. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 169–180, 2001

Molecular dynamics study of phase transition and nucleation in supercooled clusters of potassium iodide

In a series of molecular dynamics (MD) runs on (KI) 108 clusters, the Born–Mayer–Huggins potential function is employed to study structural, energetic, and kinetic aspects of phase change and the homogeneous nucleation of KI clusters. Melting and freezing are reproducible when clusters are heated and cooled. The melted clusters are not spherical in shape no matter the starting cluster is cubic or spherical. Quenching a melted (KI) 108 cluster from 960 K in a bath with temperature range 200–400 K for a time period of 80 ps both nucleation and crystallization are observed. Nucleation rates exceeding 10 36 critical nuclei m −3 s −1 are determined at 200, 250, 300, 350, and 400 K. Results are interpreted in terms of the classical theory of nucleation of Turnbull and Fisher and of Buckle. Interfacial free energies of the liquid–solid phase derived from the nucleation rates are 7–10 mJ m −2. This quantity is ∼0.19 of the heat of transition per unit area from solid to liquid, or about two-thirds of the corresponding ratio which Turnbull proposed for freezing transition. The temperature dependence of σ sl( T) of (KI) 108 clusters can be expressed as σ sl( T)∝ T 0.34.

Structural properties and medium-range order in calcium-metasilicate (CaSiO3) glass: A molecular dynamics study

Structural properties and medium-range order (MRO) in calcium metasilicate (CaSiO3) glass are investigated at different concentrations of calcium oxide through the molecular dynamics technique. Calculations are based on the Born–Mayer–Huggins potential, and show that the experimental Ca–Ca partial structure factor, which documents the existence in the glass of Ca MRO, can qualitatively be reproduced within such a model. The characteristics of Ca MRO are then examined in the context of the overall structure of the system. At equimolar concentrations of CaO and SiO2, the simulation evidentiates the formation in the glass of clusters of CaO6 octahedra in which Ca ions are roughly lying on a plane, in a configuration that closely resembles the one of crystalline CaSiO3. On the other hand, the ‘network’ structure and MRO of pure SiO2 glass appear sensibly affected by the presence of Ca ions, with considerable loose of connectivity between SiO4 tetrahedral units, and reduction of the first sharp diffraction peak in the neutron structure factor. The q-space investigation of charge–charge correlations signals the presence of medium-range charge ordering in the calcium vs oxygen ion distribution, at a wave vector equal to that associated to Ca MRO. The meaning and implications of this result are discussed.

Structural and Dynamical Properties of an LiCl · 3H2O Solution

An MD simulation of an 18.5 molal LiCl aqueous solution was performed with the flexible Bopp-Jancso-Heinzinger model for water, ion-water pair potentials derived from ab initio calcula­tions and the ion-ion interactions described by a potential of Born-Mayer-Huggins (BMH) type. The comparison with a simulation of the same system, where the ion-ion interactions were described by a (12-6) Lennard-Jones + Coulomb potential, demonstrates that such a change affects not only the ion-ion but also the ion-water radial distribution functions significantly, and that the results with the BMH potential conform better to X-ray results. The self-diffusion coefficients for water and the ions are found to be lower by almost one order of magnitude compared with dilute solutions, in good agreement with experimental results. The spectral densities of the hindered translational motions as well as those of the librations and the internal vibrations of the water molecules have been calculated from the simulations through the corresponding velocity autocorrelation functions.