Computer Physics Reports最新文献

Practical solutions of the inverse problem of scattering in molecular physics are reviewed. Methods are presented both for extracting the interaction potential from the S-matrix or its semiclassical analogue the deflection function and for inverting the cross sections to these functions. Exact quantum mechanical methods and methods in the semiclassical or the high energy approximation are available for elastic scattering data. Procedures for inelastic cross sections are discussed for symmetric exchange processes, electronic and rotational excitation. Finally the computational procedures for the preparation of the input data including necessary deconvolution processes and for the construction of the S-matrix and the potential are presented. Only methods which were applied to real data or for which at least simulated examples are available are discussed and illustrated by suitable examples.

This paper is a review of the method of constraints. The method was devised to carry out Molecular Dynamics simulations of complex molecular systems with some internal degrees of freedom frozen, in terms of atomic Cartesian coordinates. The method has been subsequently generalized to treat all kinds of holonomic constraints and has been adapted to the more recent dynamical simulations in ensembles different from the microcanonical one. We start by deriving the statistical-mechanical formalism for these systems. We then proceed to derive the equations of motion. We conclude with a detailed discussion of the relevant MD algorithms. Some technical details on the FORTRAN code are presented in an appendix.

The purpose of this paper is to review particle stimulation models and how they have been applied to study rf heating and current drive. The paper is divided into two parts. The first part will review the mathematical framework. The purpose is, first, to introduce the non-specialist to this kind of model. Secondly, I wish to point out the numerical problems, how to avoid them, and what constraints the avoidance puts on these kinds of models. In the second part of this paper, I will review how particle simulations have been applied to rf heating and current drive, in order to illustrate when such models might be appropriate to use.

This paper presents numerical methods developed for the calculation of global wave solutions in cold plasmas, in connection with rf heating in the Alfvén and ion Cyclotron Range Frequency. Both one-dimensional and two-dimensional geometries are treated, with special emphasis on the toroidal geometry. A scheme based on a variational formulation and the use of finite hybrid elements is presented in detail. The numerical properties of the computational model are carefully examined. It is shown that an approximate solution with good convergence properties in an exact geometry can be obtained.

This article reviews theoretical and numerical study on the global structure of Alfvén and ICRF waves in the high temperature plasmas confined in tokamaks. The kinetic theory of the wave equation in an inhomogeneous and dispersive medium is developed. The wave equation is solved as a boundary value problem to provide a consistent description of the excitation by an antenna, propagation and absorption of the rf waves. The wave forms, power deposition profile, power partition by plasma species, and the antenna impedance are obtained. The numerical procedure and accuracy of the solution as well as the computational performance are also discussed.