Search results for "Radial distribution"
showing 10 items of 40 documents
On the Structure of Amorphous Metals
2005
A generalized Newton iteration for computing the solution of the inverse Henderson problem
2020
We develop a generalized Newton scheme IHNC for the construction of effective pair potentials for systems of interacting point-like particles.The construction is made in such a way that the distribution of the particles matches a given radial distribution function. The IHNC iteration uses the hypernetted-chain integral equation for an approximate evaluation of the inverse of the Jacobian of the forward operator. In contrast to the full Newton method realized in the Inverse Monte Carlo (IMC) scheme, the IHNC algorithm requires only a single molecular dynamics computation of the radial distribution function per iteration step, and no further expensive cross-correlations. Numerical experiments…
Ab Initio Liquid Water Dynamics in Aqueous TMAO Solution
2015
Ab initio molecular dynamics (AIMD) simulations in trimethylamine N-oxide (TMAO)-D2O solution are employed to elucidate the effects of TMAO on the reorientational dynamics of D2O molecules. By decomposing the O-D groups of the D2O molecules into specific subensembles, we reveal that water reorientational dynamics are retarded considerably in the vicinity of the hydrophilic TMAO oxygen (O(TMAO)) atom, due to the O-D···O(TMAO) hydrogen-bond. We find that this reorientational motion is governed by two distinct mechanisms: The O-D group rotates (1) after breaking the O-D···O(TMAO) hydrogen-bond, or (2) together with the TMAO molecule while keeping this hydrogen-bond intact. While the orientatio…
Neural Network Approach for Characterizing Structural Transformations by X-Ray Absorption Fine Structure Spectroscopy
2018
AIF acknowledge support by the US Department of Energy, Office of Basic Energy Sciences under Grant No. DE-FG02 03ER15476. AIF acknowledges support by the Laboratory Directed Research and Development Program through LDRD 18-047 of Brookhaven National Laboratory under U.S. Department of Energy Contract No. DE-SC0012704 for initiating his research in machine learning methods. The help of the beamline staff at ELETTRA (project 20160412) synchrotron radiation facility is acknowledged. RMC-EXAFS and MD-EXAFS simulations were performed on the LASC cluster-type computer at Institute of Solid State Physics of the University of Latvia.
Optimal calculation of the pair correlation function for an orthorhombic system
2012
We present a new computational method to calculate arbitrary pair correlation functions of an orthorombic system in the most efficient way. The algorithm is demonstrated by the calculation of the radial distribution function of shock compressed liquid hydrogen.
Investigating the cooling rate dependence of amorphous silica: A computer simulation study
1996
We use molecular dynamics computer simulations to study the dependence of the properties of amorphous silica on the cooling rate with which the glass has been produced. In particular we show that the density, the glass transition temperature, the radial distribution function and the distribution of the size of the rings depend on the cooling rate.
Density functional study of amorphous, liquid and crystalline Ge(2)Sb(2)Te(5): homopolar bonds and/or AB alternation?
2008
The amorphous, liquid and crystalline phases of the phase change material Ge(2)Sb(2)Te(5) (GST) have been studied by means of density functional/molecular dynamics simulations. The large sample (460 atoms and 52 vacancies in the unit cell) and long simulations (hundreds of picoseconds) provide much new information. Here we extend our original analysis (2007 Phys. Rev. B 76 235201) in important ways: partial coordination numbers and radial distribution functions, bond angle distributions, new local order parameters, vibration frequencies, and the charges on atoms and vacancies. The valence band densities of states in amorphous and crystalline GST are compared with ones from x-ray photoemissi…
Scaling theory for radial distributions of star polymers in dilute solution in the bulk and at a surface, and scaling of polymer networks near the ad…
1991
Monomer density profiles ρ(r) and center–end distribution functions g(rCE) of star polymers are analyzed by using a scaling theory in arbitrary dimensions d, considering dilute solutions and the good solvent limit. Both the case of a free star in the bulk and of a center‐adsorbed star at a free surface are considered. In the latter case of a semi‐infinite problem, a distinction is made between repulsive walls, attractive walls—where for large arm length l the configuration of the star is quasi‐(d−1) dimensional—, and ‘‘marginal walls’’ where for l→∞ the transition from d‐dimensional structure occurs. For free stars, ρ(r) behaves as r−d+1/ν for small r, where ν is the exponent describing the…
Monte Carlo simulation of many-arm star polymers in two-dimensional good solvents in the bulk and at a surface
1991
A Monte Carlo technique is proposed for the simulation of statistical properties of many-arm star polymers on lattices. In this vectorizing algorithm, the length of each arml is increased by one, step by step, from a starting configuration withl=1 orl=2 which is generated directly. This procedure is carried out for a large sample (e.g., 100,000 configurations). As an application, we have studied self-avoiding stars on the square lattice with arm lengths up tol max=125 and up tof=20 arms, both in the bulk and in the geometry where the center of the star is adsorbed on a repulsive surface. The total number of configurations, which behaves asN∼l γ G–1μ fl , whereμ=2.6386 is the usual effective…
Ion size effects on the electrokinetic flow in nanoporous membranes caused by concentration gradients
2003
The space charge model (SCM) relies on the Poisson−Boltzmann (PB) equation, and hence on the assumption of negligible ion size effects, to calculate the radial distribution of the electrical potent...