Loose-coupling method

Codes of block waveform relaxation methods and of block Jacobi-Newton type methods have been tested on sequential machines. At present the parallel case is simulated by these codes. In case of loosely coupled subproblems promising results have been achieved. 

For the majority of atomic and small molecule systems at equilibrium in the (N,P,T) ensemble (P is the pressure tensor) it is widely accepted that the most rigorous approach is to use the controlled pressure technique proposed by Rahman and Parrinello (RP) in conjunction with the Nose-Hoover thermostat.However, the choice of method must take careful account of the material we wish to study, how it is modeled and any external perturbations which we wish to apply. For polymers the Berendsen loose-coupling controlled pressure MD technique is a good compromise. Although the theoretical basis of this method has been criticised in practice it has been found that to within statistical uncertainties first-order properties are the same as those obtained by more rigorous approaches. 

The simplest way to perform molecular dynamics calculations at a desired pressure p" is by loose coupling to a pressure bath . This method is well known for liquids, but for a crystal the situation is more complex due to the anisotropy of the pressure. After each time step At in the simulation all coordinates are scaled by the transformation = r - - Dr with... 

Tool-spanning method fragments (plan contexts) offered as guidance alternatives inside a fully process-integrated tool, can couple it with a loosely-process integrated one, and allow control and/or information flow from one to the other. 

In heterogeneous electron transfer experiments, the gold electrode with a monolayer film is placed in contact with the solution containing a redox couple [such as Fe(CN)63-/Fe(CN)64- etc.]60-63. The shape of the cyclic voltammogram depends on how effectively the monolayer blocks access for the redox probe to the electrode surface. This method is therefore invaluable for permeability studies. Absence of redox waves close to the formal potential of the probe indicates that the monolayer is completely impermeable for redox probe species. On the other hand, the presence of a redox wave shows either that the monolayer is loosely packed and easily penetrated by external molecules, or the presence of numerous defects and pin-holes in the monolayer. 

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