Quantum Sutton-Chen Potential Research Articles

Size and shapes effect on structural and phonon density of state in Ir nanoparticle and mechanical properties of Ir metal

Density Functional Theory (DFT) calculations were performed to assess the mechanical properties of an Ir metal nanocluster. The properties under investigation encompassed the bulk modulus, Poisson ratio, elastic shear modulus, and binding energy. The stability of the nanocluster was explored across various shapes, including icosahedron, octahedron, and truncated octahedron, with consideration given to different cluster sizes. The DFT results unveiled a general mechanism for amorphization in the Ir nanocluster of size 55, involving rosette-like structural transformations at the fivefold vertex. Additionally, Phonon Density of States (PDOS) was computed for the core, surface, and total atoms of Ir nanoclusters with sizes 38, 55, and 75, as well as for the Ir bulk structure. These calculations were carried out using both Quantum Sutton-Chen potential (QSC) and Gupta potential models through molecular dynamics (MD) methods. The analysis of the phonon density of states revealed that the contributions of two main peaks in low and high frequencies were associated with the surface and core atoms, respectively. Furthermore, the extension of the phonon density of states was performed for larger-sized Ir nanoclusters. Significantly, the QSC potential was utilized to investigate the adsorption of main peaks and their trends for the phonon density of states in the Ir bulk structure. The results obtained from this method were found to be in agreement with experimental data derived from cold neutron and multidetector time-of-flight spectrometer phonon measurements.

Phonon spectra and temperature variation of bulk properties of Cu, Ag, Au and Pt using Sutton–Chen and modified Sutton–Chen potentials

Three potentials of the Finnis–Sinclair type are studied with regard to their suitability for predicting bulk thermal and elastic properties of fcc metals Cu, Ag, Au and Pt over a wide temperature range. We start with a particular parametrization of the Finnis–Sinclair model known as the Sutton–Chen potential and a later version of the same, known as the quantum Sutton–Chen potential. The quasiharmonic lattice dynamics method is used to study the temperature variation of the thermodynamic properties. Both models are found to yield poor results for thermal expansion, which can be traced to rapid softening of transverse phonon frequencies with increasing lattice parameter. The form of the Sutton–Chen potential is modified here to seek improvement in the agreement between quasiharmonic calculations and experimental data. It is found that the modified potential better predicts bulk properties in nearly all cases studied. Significant improvement is seen over the Sutton–Chen potential, while lesser but still substantial improvement is observed over the Quantum-Sutton Chen potential.

Disorder effect on heat capacity, self-diffusion coefficient, and choosing best potential model for melting temperature, in gold–copper bimetallic nanocluster with 55 atoms

Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models.

The Statistical Modeling of the Platinum Nanoparticles in the Transition Area from the Five-fold Symmetry Structure to the Crystal Lattice

This paper deals with the atom energy mean value of the platinum nanoparticles of various size (from 300 to 3000 atoms that approximately corresponds to the transition threshold from the icosahedral structure to the face-centered cubic one) on the face-centered cubic lattice and on the five-fold symmetry one, with the application of the modified Metropolis algorithm based on the Monte-Carlo method. When calculating the energy the quantum Sutton-Chen potential is used.

High pressure molecular dynamics simulation of Au-x%Ni alloys

The aim of this investigation was to calculate thermodynamics properties of Au-x%Ni (atomic percent) by molecular dynamics (MD) simulation technique under high pressure. The many body quantum Sutton-Chen potential was employed to obtain cohesive energy and force experienced by every atom at the isothermal, isobaric (NPT) ensemble. The effect of pressure and Ni concentration on the physical properties, including cohesive energy, melting temperature, isobaric heat capacity, redial distribution function, and order parameter were calculated for Au-x%Ni alloys. The obtained MD results show that cohesive energy and melting temperature increase upon pressure increase. In addition, linear thermal expansion as well as isobaric heat capacity decreases with increasing pressure. Moreover, the phase diagrams of Au-x%Ni alloys were plotted at different pressure showing melting points as a function of Ni concentration.

Formation and Evolution of Metastable bcc Phase during Solidification of Liquid Ag: A Molecular Dynamics Simulation Study

On the basis of the quantum Sutton-Chen potential, the rapid solidification processes of liquid silver have been studied by molecular dynamics simulation for four cooling rates. By means of several analysis methods, the competitions and transitions between microstructures during the cooling processes have been analyzed intensively. It is found that there are two phase transitions in all simulation processes. The first one is from liquid state to metastable (transitional) body-centered cubic (bcc) phase. The initial crystallization temperature T(ic) increases with the decrease of the cooling rate. The second one is from the transitional bcc phase to the final solid phase. This study validates the Ostwald's step rule and provides evidence for the prediction that the metastable bcc phase forms first from liquid. Further analyses reveal that the final solid at 273 K can be a mixture of hexagonal close-packed (hcp) and face-centered cubic (fcc) microstructures with various proportions of the two, and the slower the cooling rate is, the higher proportion the fcc structure occupies.

Structural, thermodynamical, and transport properties of undercooled binary Pd–Ni alloys

The solidification properties of Pd–Ni alloys are studied with constant-pressure, constant-temperature (TPN), and constant-volume, constant-temperature (TVN) molecular dynamics simulations based on quantum Sutton–Chen potential. Whether the system forms the glass structure or it transforms into ordered state is checked at various cooling rates ranging from 10 K/ps to 0.05 K/ps. The effect of concentration and cooling rates on the glass transition temperature is examined. The behavior of heat capacity at constant pressure ( C p ) in glass and liquid state is analyzed. Glass forming ability is also investigated by means of transport properties such as diffusion and shear viscosity. Strength parameter calculated from shear viscosity data indicates fragile-liquid behavior. The results show that the mismatch in atomic size and having the eutectic composition are important factors for glass forming.

Molecular dynamics simulations of the structural and dynamic properties of graphite-supported bimetallic transition metal clusters

Molecular dynamics simulations were carried out for $\mathrm{Pd}\ensuremath{-}\mathrm{Pt}$, $\mathrm{Pd}\ensuremath{-}\mathrm{Rh}$, and $\mathrm{Pd}\ensuremath{-}\mathrm{Cu}$ nanoclusters supported on a static graphite substrate using the quantum Sutton-Chen potential for the metal-metal interactions. The graphite substrate was represented as layers of fixed carbons sites and modeled with the Lennard-Jones potential model. Metal-graphite interaction potentials obtained by fitting experimental cohesive energies were utilized. Monte Carlo simulations employing the bond order simulation model were used to generate initial configurations. The melting temperatures for bimetallic nanoclusters of varying composition were estimated based on variations in thermodynamic properties such as potential energy and heat capacity. Melting transition temperatures were found to decrease with increasing Cu (for $\mathrm{Pd}\ensuremath{-}\mathrm{Cu}$) and Pd (for $\mathrm{Pd}\ensuremath{-}\mathrm{Pt}$ and $\mathrm{Pd}\ensuremath{-}\mathrm{Rh}$) concentrations and are at least $100\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}200\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ higher than those of the same-sized free clusters. Density distributions perpendicular to the surface and components of the velocity autocorrelation functions in the plane of the surface indicate that one of the metals in the bimetallic nanoclusters wets the graphite surface more, and that this weak graphite substrate is able to structure the melted fluid in the first few monolayers. The wetting characteristics are dictated by the delicate balance between metal-metal and metal-graphite interactions. Components of velocity-autocorrelation functions characterizing diffusion of constituent atoms in these bimetallics suggest greater out-of-plane movement, which increases with Cu (for $\mathrm{Pd}\ensuremath{-}\mathrm{Cu}$) and Pd (for $\mathrm{Pd}\ensuremath{-}\mathrm{Rh}$ and $\mathrm{Pd}\ensuremath{-}\mathrm{Pt}$) concentrations. Deformation parameters showed that the core (Pd in $\mathrm{Pd}\ensuremath{-}\mathrm{Cu}$, Rh in $\mathrm{Pd}\ensuremath{-}\mathrm{Rh}$ and Pt in $\mathrm{Pd}\ensuremath{-}\mathrm{Pt}$) atoms diffuse out and the surface-segregated (Cu in $\mathrm{Pd}\ensuremath{-}\mathrm{Cu}$, Pd in $\mathrm{Pd}\ensuremath{-}\mathrm{Rh}$ and $\mathrm{Pd}\ensuremath{-}\mathrm{Pt}$) atoms diffuse into the nanoclusters upon melting. Near linear dependence of melting temperature on composition was found for unsupported clusters in our recent work, which results from the balance between the extent of surface melting and the radius of remaining solid core. Nonlinear dependence was found in these supported clusters, as a result of reduced surface melting at higher Pd concentrations, due to the substrate effect. Shell-based diffusion coefficients for layers perpendicular to the graphite substrate suggest surface melting to start from the cluster surface experiencing least influence of the graphite field. Surface melting was seen in all three nanoclusters, with calculated bond orientational order parameters revealing the order of $\mathrm{Pd}\ensuremath{-}\mathrm{Cu}>\mathrm{Pd}\ensuremath{-}\mathrm{Pt}>\mathrm{Pd}\ensuremath{-}\mathrm{Rh}$, for onset of melting. Cluster snapshots on the graphite substrate and calculated cluster diffusion coefficients indicate these nanoclusters to diffuse as single entities with very high diffusivities, consistent with experimental observations.

Liquid properties of Pd–Ni alloys

Liquid properties of Pd–Ni metal alloys are computed by molecular dynamics (MD) simulation with the use of quantum Sutton–Chen potential (Q-SC) model. The thermodynamical, structural, and transport properties of the alloy are investigated. The melting temperatures for Pd–Ni system are predicted. The temperature and concentration dependence of diffusion coefficient and viscosity are reported. The transferability of the potential is tested by simulating the liquid state. The values of melting point are in excellent agreement with the experiment. Comparison of calculated structural and dynamical properties with the available experiments and other calculations shows satisfactory consistency.

Liquid properties of Pd?Ni alloys

Liquid properties of Pd–Ni metal alloys are computed by molecular dynamics (MD) simulation with the use of quantum Sutton–Chen potential (Q-SC) model. The thermodynamical, structural, and transport properties of the alloy are investigated. The melting temperatures for Pd–Ni system are predicted. The temperature and concentration dependence of diffusion coefficient and viscosity are reported. The transferability of the potential is tested by simulating the liquid state. The values of melting point are in excellent agreement with the experiment. Comparison of calculated structural and dynamical properties with the available experiments and other calculations shows satisfactory consistency.