Article

Canonical dynamics: Equilibrium phase-space distribution

Physical Review A (Impact Factor: 2.99). 04/1985; 31(3):1695-1697. DOI: 10.1103/PhysRevA.31.1695
Source: PubMed

ABSTRACT Nose has modified Newtonian dynamics so as to reproduce both the canonical and the isothermal-isobaric probability densities in the phase space of an N-body system. He did this by scaling time (with s) and distance (with V¹D/ in D dimensions) through Lagrangian equations of motion. The dynamical equations describe the evolution of these two scaling variables and their two conjugate momenta p/sub s/ and p/sub v/. Here we develop a slightly different set of equations, free of time scaling. We find the dynamical steady-state probability density in an extended phase space with variables x, p/sub x/, V, epsilon-dot, and zeta, where the x are reduced distances and the two variables epsilon-dot and zeta act as thermodynamic friction coefficients. We find that these friction coefficients have Gaussian distributions. From the distributions the extent of small-system non-Newtonian behavior can be estimated. We illustrate the dynamical equations by considering their application to the simplest possible case, a one-dimensional classical harmonic oscillator.

Download full-text

Full-text

Available from: William Graham Hoover, Aug 07, 2014
4 Followers
 · 
347 Views
  • Source
    • "Rahman barostat with coupling time constants of 0.1 and 1.0 ps, in respective order (Nosé 1984; Hoover 1985; Parrinello and Rahman 1981). The temperatures of the solute and solvent were controlled independently , and the temperature was chosen to match the one used in industrial processes (Viikari et al. 2007). "
    Cellulose 07/2015; DOI:10.1007/s10570-015-0705-0 · 3.03 Impact Factor
    • "The Nose–Hoover thermostat [36] [37] was used to maintain constant temperature. Van der Waals and short-range electrostatic interactions were truncated at 1.5 nm; long-range electrostatic interactions were calculated by the particle mesh Ewald (PME) method [38] [39]. The LINCS algorithm [40] was employed to restrict all bond lengths. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the present work, solvation of the salicylic acid in pure, methanol-modified and water-modified (by adding 0.035 methanol or 0.0079 water mole fraction) supercritical carbon dioxide (sc-CO2) at 318 K and 0.7 g/cm3 has been studied by computer simulation techniques. It was shown that solvation of salicylic acid in pure sc-CO2 is governed by electron donor-acceptor interactions and proceeds more slowly than in modified sc-CO2, where salicylic acid forms solvate complex with co-solvent by means of hydrogen bonding through carboxyl group. Salicylic acid hydroxyl group participates only in intramolecular hydrogen bond and does not interact with solvent molecules. The salicylic acid – co-solvent complexes are stable: the duration of their existence is much higher than lifetime of other hydrogen bonds in the fluid. The behavior of two co-solvents is different: methanol exists in the form of monomers and hydrogen-bonded dimers in the supercritical fluid, the water molecules tend to form microclusters with spatially-branched structure.
    Journal of Supercritical Fluids The 06/2015; DOI:10.1016/j.supflu.2015.06.016 · 2.57 Impact Factor
  • Source
    • "We stress that rather than statistically robust insight into the real-time dynamics of the optimized adlayer (which would require larger simulation cells, longer MD trajectories, and rigorous canonical ensemble sampling [80]), the main target of this study was to use NVT MD equilibration, followed by structural relaxation, to identify lower Eform minima potentially missed by the initial screening. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To explore the potential of molecular gas treatment of freshly cut lithium foils in non-electrolyte based passivation of high energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of molecular gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated. The simulations suggest that exposure to different molecular gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages <= 1 mono-layer. The substantial Li->adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers.
Show more