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Energy, constant

For an ideal gas and a diathemiic piston, the condition of constant energy means constant temperature. The reverse change can then be carried out simply by relaxing the adiabatic constraint on the external walls and innnersing the system in a themiostatic bath. More generally tlie initial state and the final state may be at different temperatures so that one may have to have a series of temperature baths to ensure that the entire series of steps is reversible. [Pg.338]

Consider, at t = 0, some non-equilibrium ensemble density P g(P. q°) on the constant energy hypersurface S, such that it is nonnalized to one. By Liouville s theorem, at a later time t the ensemble density becomes ((t) t(p. q)), where q) is die function that takes die current phase coordinates (p, q) to their initial values time (0 ago the fimctioii ( ) is uniquely detemiined by the equations of motion. The expectation value of any dynamical variable ilat time t is therefore... [Pg.388]

The are many ways to define the rate of a chemical reaction. The most general definition uses the rate of change of a themiodynamic state function. Following the second law of themiodynamics, for example, the change of entropy S with time t would be an appropriate definition under reaction conditions at constant energy U and volume V ... [Pg.759]

Equation (ASA. 110) represents the canonical fonn T= constant) of the variational theory. Minimization at constant energy yields the analogous microcanonical version. It is clear that, in general, this is only an approximation to the general theory, although this point has sometimes been overlooked. One may also define a free energy... [Pg.784]

Also we must bear in mind that the advancement of the coordinates fidfds two fiinctions (i) accurate calculation of dynamical properties, especially over times as long as typical correlation times x (ii) accurately staying on the constant-energy hypersurface, for much longer times Exact time reversibility is highly desirable (since the original equations... [Pg.2250]

There are tln-ee general approaches to conducting MD at constant temperature rather than constant energy. [Pg.2261]

One property of the exact trajectory for a conservative system is that the total energy is a constant of the motion. [12] Finite difference integrators provide approximate solutions to the equations of motion and for trajectories generated numerically the total energy is not strictly conserved. The exact trajectory will move on a constant energy surface in the 61V dimensional phase space of the system defined by. [Pg.300]

Because of liiTi itation s iu corn pu ter poxver an d time, it is frequen tly impractical to run a constant energy molecular dynaniics simulation. -Several approxirn ation s to th e eu ergy (usually to th e poteu -tial en ergy) are possible, wh ieh require m odifyiri g th e Ham ilto-... [Pg.71]

For constant energy simulations without temperature regulation, use heating steps of about 0.5 ps and a healing time of 20-30 ps. In gen eral, short h eating tim es and large temperature steps perturb th e initial system m ore than Ion gcr heating times and small tern -perature steps. [Pg.88]

Because of limitations in computer power and time, it is frequently impractical to run a constant energy molecular dynamics simulation. Several approximations to the energy (usually to the potential energy) are possible, which require modifying the Hamilto-... [Pg.71]

If there is no external temperature control (using a simulated constant temperature bath), molecular dynamics simulations are constant energy. [Pg.77]

For a conformation in a relatively deep local minimum, a room temperature molecular dynamics simulation may not overcome the barrier and search other regions of conformational space in reasonable computing time. To overcome barriers, many conformational searches use elevated temperatures (600-1200 K) at constant energy. To search conformational space adequately, run simulations of 0.5-1.0 ps each at high temperature and save the molecular structures after each simulation. Alternatively, take a snapshot of a simulation at about one picosecond intervals to store the structure. Run a geometry optimization on each structure and compare structures to determine unique low-energy conformations. [Pg.78]

In most electron spectroscopic analyses, the kinetic energies of the electrons entering the analyzer are retarded to either a constant energy or by a constant factor. These approaches lead to two modes of operation the constant analyzer energy (CAE) mode and the constant retard ratio (CRR) mode. [Pg.283]

Of all the fossil fuels, the use of natural gas results ia the formation of the least amouat of CO2 per unit of heat energy produced. On a constant energy basis, natural gas combustion produces approximately 30% less CO2 than Hquid petroleum fuels and approximately 45% less CO2 than coal and other soHd fossil fuels. [Pg.174]

Here Q is the amount of heat contained per unit volume in the substrate, jc is the distance down into the substrate, and t is the time of inadiation. The solutions of this equation depend on the physical conditions of the uradiation. Thus if the surface is subject to a constant energy supply, Qq, the solution is... [Pg.78]

An alternative method, proposed by Andersen [23], shows that the coupling to the heat bath is represented by stochastic impulsive forces that act occasionally on randomly selected particles. Between stochastic collisions, the system evolves at constant energy according to the normal Newtonian laws of motion. The stochastic collisions ensure that all accessible constant-energy shells are visited according to their Boltzmann weight and therefore yield a canonical ensemble. [Pg.58]

Figure 4 (a) Solving Newton s equations of motion at constant energy allows the molecule to... [Pg.261]

In XPS the photoelectrons are retarded to a constant energy, called the pass energy, as they approach the entrance slit. If this were not done, Eq. (2.5) shows that to achieve an absolute resolution of 1 eV at the maximum kinetic energy of approximately 1500 eV (using A1 Ka radiation), and with a slit width of 2 mm, would require an analyzer with an average radius of about 300 cm, which is impracticable. Pass energies are selected in the range 20-100 eV for XPS, which enables the analyzer to be built with a radius of 10-15 cm. [Pg.14]

Eq. (1) would correspond to a constant energy, constant volume, or micro-canonical simulation scheme. There are various approaches to extend this to a canonical (constant temperature), or other thermodynamic ensembles. (A discussion of these approaches is beyond the scope of the present review.) However, in order to perform such a simulation there are several difficulties to overcome. First, the interactions have to be determined properly, which means that one needs a potential function which describes the system correctly. Second, one needs good initial conditions for the velocities and the positions of the individual particles since, as shown in Sec. II, simulations on this detailed level can only cover a fairly short period of time. Moreover, the overall conformation of the system should be in equilibrium. [Pg.485]


See other pages where Energy, constant is mentioned: [Pg.109]    [Pg.284]    [Pg.319]    [Pg.366]    [Pg.367]    [Pg.367]    [Pg.367]    [Pg.370]    [Pg.77]    [Pg.86]    [Pg.94]    [Pg.400]    [Pg.535]    [Pg.77]    [Pg.86]    [Pg.86]    [Pg.87]    [Pg.88]    [Pg.94]    [Pg.94]    [Pg.367]    [Pg.367]    [Pg.248]    [Pg.2291]    [Pg.127]    [Pg.166]   
See also in sourсe #XX -- [ Pg.86 ]

See also in sourсe #XX -- [ Pg.86 ]

See also in sourсe #XX -- [ Pg.626 ]




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A Closed System of Constant Internal Energy and Volume

Activation Energy and Pre-Exponential Factors in the Reaction Rate Constant Expression

Activation Energy and Reaction Rate Constant

Activation Energy and Temperature Dependence of Rate Constants

Activation energy and rate constant

Activation energy and specific rate constant

Activation energy constants

Activation free energy constants

Activation free energy forward rate constant

Activation free energy heterogeneous rate constant

Activation free energy rate constant

Apparent activation energy rate constant

Apparent equilibrium constant transformed Gibbs energies

Atomic charges, dielectric constant electrostatic energies

Attractive interaction energy Hamaker constant

Biacetyl, energy transfer rate constants

Bond dissociation energy force constants

Cell Potential, Free Energy, and the Equilibrium Constant

Cohesive energy density, dependence constant

Constant Energy and Length

Constant Energy, Temperature, or Pressure

Constant analyzer energy

Constant energy hypersurface

Constant kinetic energy

Constant self-energy

Constant temperature/energy

Constant-energy ellipsoid

Constant-energy surface

Contour, of constant energy

Different Theories of Bimolecular Rate Constants Experimental Activation Energies

Dissociation constant final structure energy

Dissociation energy spectroscopic constants

Elastic constants and anchoring energies

Electron transfer rate constants, function free-energy change

Electrostatic energy Madelung constants

Electrostatic energy, variation with dielectric constant

Energy Loss Expressed in Universal Constants

Energy Minima, Force Constants and Structure Correlation

Energy Planck’s constant

Energy constant-volume

Energy constant-volume condition

Energy constants, Wilson

Energy controlled rate constant

Energy equilibrium constant

Energy inhibitor constant

Energy transfer , photosynthetic reaction rate constants

Enthalpy, Free Energy, and Equilibrium Constant

Equilibrium Constants Relation to Energy and Entropy Changes

Equilibrium constant Gibbs free energy

Equilibrium constant Gibbs free energy relationship

Equilibrium constant and Gibbs energy

Equilibrium constant free energy

Equilibrium constant free energy and

Equilibrium constant free energy change

Equilibrium constant relationship to Gibbs energy chang

Equilibrium constant standard Gibbs energy

Equilibrium constant standard free energy

Equilibrium constant, standard free energy related

Equilibrium constants Experimental" correlation energy

Equilibrium constants relationship with Gibbs energy change

Equilibrium constants relationship with standard Gibbs energy

Excitation energy spectroscopic constants

Fluorescence resonance energy transfer decay constant

Free energy and the equilibrium constants

Free energy change and the equilibrium constant

Free energy perturbations equilibrium constants

Free energy relationship with equilibrium constant

Free energy, relation to equilibrium constant

Gibbs Free Energy, Chemical Potential, and the Equilibrium Constant

Gibbs energies apparent equilibrium constant derivation

Gibbs energy change and equilibrium constant

Gibbs energy change equilibrium constant

Gibbs energy reaction, calculation constant

Gibbs free energy and equilibrium constant

Gibbs free energy constant

Gibbs free standard energy rate constants

Homological Properties of Constant-Energy Surfaces

Internal energy constant-pressure processes

Internal energy constant-volume

Internal energy, changes at constant

Kinetics Based on Rate Constants or Energies

Lattice Energy and Madelung Constant

Lattice Energy and the Madelung Constant

Length-energy correlation constants

Linear free energy relationships Involving rate constants

Magnetic anisotropy energy constant

Minimum energy coordinates interaction constants

Molecular Dynamics with Constant Energy

Molecular dynamics constant energy

Nuclear energy coupling constant

Organic reaction mechanisms energy difference, equilibrium constant

Partition function, potential energy surfaces rate constants

Potential energy constant

Potential energy surface dielectric constant

Potential energy surfaces force-constant matrix

Potential energy, anharmonic terms interaction constants

Proportionality constant, potential energy

Pseudo-energy force constants

Quenching rate constants, free energy

Quenching rate constants, free energy dependence

RRKM rate constant zero-point energy

Radius constant energy

Rale constants energies

Rate constant activation energy

Rate constant energy dependence

Rate constant nonradiative energy transfer

Rate constant resonance energy transfer

Rate constants and activity energies

Rate constants and lifetimes of reactive energy states

Rate constants energy

Rate constants for triplet energy transfer

Rate constants linear free-energy relationship

Rate constants potential energy surfaces

Reaction rate constant energy-averaged

Reorganizational energy constants

Resonance energies constants

Rotational Constants. Potential Energy Functions

Rotational energy levels constants)

Stability constants crystal field stabilization energy

Standard Gibbs energy change equilibrium constant

Standard-state Free Energies, Equilibrium Constants, and Concentrations

State constant energy

Strain energy from equilibrium constants

Strength of binding Dissociation constants, Gibbs energy

Surface energy and Hamaker constant

Temperature Dependence of Rate Constants Activation Energies

Temperature versus Constant Energy

The Madelung Constant and Crystal Lattice Energy

Thermodynamic equilibrium constant relating free-energy change

Transformed Gibbs energy apparent equilibrium constants, tables

Vibrational energy relaxation coupling constants calculation

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