Many-body Potential Energy Function Research Articles

Optimisation of carbon cluster geometry using a genetic algorithm

A genetic algorithm (GA) based global optimisation procedure has been developed and used to find the most stable configurations of small carbon clusters. The GA attempts to locate the set of atomic nuclei coordinates associated with the global minimum of the potential-energy function using an analogy to Darwinian natural selection. This algorithm uses a novel encoding scheme to evolve a population of cluster geometries towards a low-energy final state. Two semi-empirical many-body potential-energy functions have been encoded for carbon interactions. The binding energies and structural forms of carbon clusters between C3 and C60 are reported. It has been shown that the algorithm can determine structures with a lower energy than those previously published using more classical local optimisation procedures. The GA can also be used to predict the global minimal energy configuration of pairwise interaction potentials.

Theoretical study of the structures and stabilities of iron clusters

An empirical many-body potential energy function, derived previously by fitting data for two allotropes of iron (bcc and fcc), has been applied to the study of the structures and relative stabilities of iron clusters with up to 671 atoms. For small clusters, growth is predicted to occur via the fusion of tetrahedral units, leading eventually to icosahedral clusters. A subset of larger clusters, with high symmetries and shell structures (so called Geometric Shell Magic Number Clusters) was studied and the stability order icosahedral > rhombic dodecahedral (bcc) > decahedral > cuboctahedral (fcc) established in the nuclearity range studied, though crossover of stability between icosahedral and (bulk-like) bcc structures is predicted to occur at around 2000 atoms.

Molecular Dynamics Simulations of Reactions between Molecules: High-Energy Particle Bombardment of Organic Films

High energy bombardment mass spectrometric techniques are becoming ever more important for organic and biological samples. Before the molecule can be detected, though, it must first be ejected. The authors have developed a molecular dynamics prescription for examining the fundamental processes important for the ejection of organic molecules during the particle bombardment event. The major advance here over previous simulations is the use of an empirical many-body potential energy function constructed for studying reactive dynamics. Specifically, bonds can be broken and reformed. For the first time, one can examine the possibility of reactions among the organic molecules. As an initial test system, the authors have investigated the 500 eV Ar bombardment of ethylidyne, C{sub 2}H{sub 3}, on Pt (111). This specific system has been studied experimentally by White and co-workers using SIMS. The authors have modeled both 0.25 and 0.50 monolayer ethylidyne coverage in order to test density effects. They find that approximately 80% of the ejected hydrocarbon species originate from a single C{sub 2}H{sub 3} adsorbate, while the others result from reactions between two C{sub 2}H{sub 3} adsorbates. A study of the internal energies of all of the ejected hydrocarbon aggregates reveals that those originating from a single C{submore » 2}H{sub 3} adsorbate are generally stable to any further fragmentation or rearrangement. Examples of common ejection mechanisms for species which originate from a single adsorbate, such as CH{sub 3}, C{sub 2}H{sub 3}, HCCH, and those which originate from more than one adsorbate, such as CH{sub 4} and H{sub 2} will be discussed.« less

A lattice dynamical study of Cu and Ni based on a new empirical many-body potential

In the present work, a recently developed empirical many-body potential-energy function (PEF) is first used, as an application, to investigate the dynamical behaviors of the face-centred-cube d-band metals, Cu and Ni. The new PEF contains both two- and three-body atomic interactions. The two-body potential is a kind of hybrid function and the three-body potential is expressed in terms of the two-body interactions. The parameters defining the PEF for the metals are computed following a procedure similar to a method given by Girifalco and Weizer. The input data for evaluating the necessary parameters are independent of the phonon frequencies and elastic constants of the metals. The phonon frequencies along the principal symmetry directions of Cu and Ni are calculated using the computed two- and three-body force constants. The results are found to be in good agreement with the corresponding experimental values.

EMPIRICAL MANY-BODY POTENTIAL ENERGY FUNCTION CALCULATION FOR LITHIUM CLUSTERS IN BCC AND FCC SURFACE SYMMETRIES, AND CHEMISORPTION ENERGY OF ATOMIC OXYGEN ON LITHIUM BCC CLUSTERS

We have investigated the structure and energetics of lithium clusters containing 3 to 10 atoms in different bcc and fcc surface symmetries, and the interaction of an oxygen atom with lithium clusters in the bcc(100) and bcc(110) surface symmetries. Calculations have been performed by using an empirical many-body potential energy function, which comprises two- and three-body atomic interactions.

An empirical many-body potential energy function constructed from pair-interactions

A new empirical potential energy function (PEF) is proposed, which is formed from pair-interactions only, and containes the many-body contributions. The PEF satisfies bulk cohesive energy and bulk stability condition. The PEF is parameterized for copper, silver, and gold elements in fcc crystal structure. The elastic constantsC11 andC12 and the bulk modulus of the elements are calculated, and the structural stability and energetics of microclusters containing 3 to 7 atoms of the same elements are investigated.

Bulk and surface properties of aluminum: a molecular-dynamics simulation

We have investigated the bulk and surface properties of aluminum using the molecular-dynamics technique. In the simulation a recently developed empirical many-body potential energy function, which contains two- and three-body atomic interactions, has been used. The bulk properties of specific heat capacity and vacancy formation energy have been calculated, and the surface properties of surface energy, surface vacancies, and adatoms on the (001) surface, have been investigated at low temperature.

An Anisotropic Polarizable Water Model: Incorporation of All-Atom Polarizabilities into Molecular Mechanics Force Fields

An anisotropic polarizable water model has been constructed using atomic polarizabilities of oxygen and hydrogen and the SPC molecular mechanics force field. The presence of polarizable interaction sites on all atoms allows treatment of dipole-dipole interactions between bonded atoms and simplifies the incorporation of polarization treatments into existing molecular mechanics force fields. The resulting many-body potential yields the correct dipole moments for the water monomer and dimer as well as molecules in the bulk. Furthermore, the model predicts structures, energies, and dynamical behavior for bulk water which are in good agreement with experimental findings. Several potential energy functions for water are currently used in computer simulations of pure water and water-solute systems. Most simulations use potentials that are pairwise additive.' Calculations with many-body potentia1s2-l6 are not common partly due to the substantial increase in computational requirements demanded by such potentials. These potentials often express the many-body component of the potential energy function in terms of atomic and molecular polarizabilities. The development of such functions and their use in simulations requires development of new molecular mechanics force fieldsz4 or reparametrization of terms in the existing force Other approaches to polarization use either additional variable point chargesg-12 or multipole expansions of the electrostatic intera~tion.~~J~ Additional many-body potentials will undoubtedly be devised as ever increasing computational ~apabilitiesl~-~ ~ encourage their use. There is a need for an all-atom, many-body potential energy function which combines polarization effects within a framework compatible with existing molecular mechanics force fields. First, many-body polarization effects are presumed to be important for describing the energetics of interfacial phenomena,20J some types of ionic2q22-26 and hydrophobic solvati~n,~~-~~ and cluster chemistry32-35 to name a few applications, although it is not yet well established for which systems polarization must be included e~plicitly.29~~~ Second, by retaining other (nonelectrostatic) components of standard molecular force fields in the polarizable potential, it may be possible to build upon the large effort that has gone into the construction of existing molecular mechanics potential functions. With the polarizable potential it becomes possible to examine the many-body nature of the electrostatic interactions. Preservation of the nonelectrostatic pairwise terms simplifies the analysis involved when comparing predictions obtained with the polarizable potential to those calculated using pairwise potentials.

Empirical many-body potential energy functions for iron

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEmpirical many-body potential energy functions for ironFei Gao, Roy L. Johnston, and John N. MurrellCite this: J. Phys. Chem. 1993, 97, 46, 12073–12082Publication Date (Print):November 1, 1993Publication History Published online1 May 2002Published inissue 1 November 1993https://doi.org/10.1021/j100148a038RIGHTS & PERMISSIONSArticle Views428Altmetric-Citations22LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

An empirical many-body potential-energy function for aluminum. Application to solid phases and microclusters

An empirical two-plus-three-body potential, developed by Murrell and co-workers [J. N. Murrell and R. A. Rodriguez-Ruiz, Mol. Phys. 71, 823 (1990)], is applied to the study of fcc aluminum. The parameters in the potential are derived by fitting the experimental phonon-dispersion curves and elastic constants. Calculations, using this potential, on a number of one-, two- and three-dimensional extended systems give results which are in quantitative agreement with recent ab initio calculations [I. J. Robertson, M. C. Payne, and V. Heine, Europhys. Lett. 15, 301 (1991)]. Calculations on small- and medium-sized aluminum clusters give cluster geometries and growth patterns which agree qualitatively with previous ab initio molecular-orbital and density-functional studies.

A Molecular Dynamics Study of Silver Microclusters

Employing a recently developed empirical many-body potential energy function, we obtained the ground-state structures of silver microclusters (N=3-9, 13) using molecular dynamics and quenching method. The present configurations for clusters (N=3-6) agree well with the available literature values, while the structures for clusters (N=7-9, 13) are newly reported. Also, we find that there is a distinct alternation between even and odd numbered neutral silver clusters with growing cluster size.

Structural stability and energetics of As, Sb and Bi microclusters: empirical many-body potential energy function calculation

The structural stability and energetics of As, Sb and Bi microclusters having 3–7 atoms have been investigated by using a recently developed empirical many-body potential energy fuction (PEF), which comprises two- and three-body atomic interactions. The PEF satisfies both bulk cohesive energy per atom and bulk structural stability exactly. It has been found that the most stable structures of As3, Sb3 and Sb4 microclusters are in linear form with D∞h symmetry, Bi7 is in hexagonal pyramid form with D6v symmetry. The rest of the microclusters prefer the planar form.

Structural stability and energetics of C, Si, and Ge microclusters: empirical many-body potential energy function calculation

The structural stability and energetics of carbon, silicon, and germanium microclusters containing 3−7 atoms have been investigated by using a recently developed empirical many-body potential energy function (PEF), which comprises two- and three-body atomic interactions. The PEF satisfies both bulk cohesive energy per atom and bulk stability exactly. It has been found that the most stable C3−4 microclusters are linear withD ∞h symmetry but C5−7 microclusters are planar withD nh symmetry. Silicon and germanium microclusters show similar structural stability. TheX n (X=Si, Ge;n=3−7) microclusters are found to be most stable in the following forms:X 3 is triangular withD 3h symmetry,X 4 is tetragonal withT d symmetry,X 5 is square pyramidal withD 4h symmetry,X 6 is bipyramidal square withO h symmetry, and finallyX 7 is square pyramidal having two atoms underneath withD 2h symmetry.

Structural Stability and Energetics of F.C.C. Metal Microclusters. Empirical Many‐Body Potential Energy Function Calculation

AbstractThe structural stability and energetics of microclusters containing 3 to 7 atoms of f.c.c. metal elements are investigated. A recently developed empirical many‐body potential function (PEF) is used in the calculations, which comprises two‐ and threebody atomic interactions. The PEF satisfies both, bulk cohesive energy and stability condition. It is found that the energetically most stable structures of microclusters are in compact form.

Empirical many-body potential energy function for silver and gold: Application to microclusters

A recently developed empirical many-body potential energy function (PEF) has been modified and parametrized for the elements silver and gold. The PEF comprises two- and three-body atomic interactions, which satisfy both the bulk cohesive energy per atom and the bulk stability exactly, and give the bulk modulus reasonably well. The structural stability and energetics of microclusters of these elements containing three to seven atoms have been investigated. It has been found that the triangular form of trimers and the three-dimensional configurations of four- to seven-atom microclusters are energetically more stable. The present cluster configurations are qualitatively in agreement with the available literature values.

Molecular-Dynamics Simulations of Collisions of Buckminsterfullerene with Diamond Surfaces

ABSTRACTWe have performed molecular dynamics simulations using a recently developed empirical many-body potential energy function to study the collision of the C60 isomer buckmin-sterfullerene with a hydrogen-terminated diamond surface. The simulations indicate that the cluster can react with the surface and has a larger probability of gaining atoms from the surface than of losing atoms to the surface. We have investigated the dependence of the reaction probability on the initial center-of-mass translational velocity of the cluster. The structures and energy distributions of the product clusters have been determined. Both inelastically and reactively scattered clusters have large amounts of internal energy which suggests that gas-phase dissociation is likely.

Role of potential-energy scaling in the low-temperature relaxation behavior of amorphous materials.

Under the assumption that the Kohlrausch-Williams-Watts (KWW) function describes relaxation near the glass transition for amorphous substances, implications are explored for the character of the many-body potential-energy function. The analysis proceeds in several stages: (1) The configuration space is uniquely divided into minimum-containing cells by a steepest-descent construction on the potential hypersurface. (2) Attention is confined to the amorphous region of configuration space by projecting out all cells containing local crystalline patterns. (3) The potential is separated into a hard-core part ${\ensuremath{\Phi}}_{c}$ and a ``soft'' remainder ${\ensuremath{\Phi}}_{s}$. (4) ${\ensuremath{\Phi}}_{s}$ is coarse grained (smoothed) over a variable scale of lengths l. (5) A master equation is used to describe the relaxation spectrum subject to the interaction smoothed over any l. The demand that KWW relaxation emerge from the last constrains the statistical topography of ${\ensuremath{\Phi}}_{s}$. Specifically it requires that on widely separated length scales, multiply branched channels of relatively modest elevation change must exist in ${\ensuremath{\Phi}}_{s}$. Furthermore, the separating barriers between these channels tend to be largest in those portions of configuration space sampled by the system at the lowest temperatures, and to scale as lnl.