PHONON program

With the advance of computing techniques classic LD programs have become more and more sophisticated. The PHONON program, provided from Daresbury Laboratory [69], is one such excellent example. PHONON uses the quasi-harmonic approximation and has a wide range of two body potentials embodied in the code. In addition, angular three-body bending potentials, four-body torsion potentials are also included. The program has been widely used for simulations of a variety of properties, such as dispersion curves, defects and surface phonons of crystalline and amorphous materials. 

The calculation of the complete phonon spectrum of Germanium is in progress. The method described in the present paper was programmed for a vector computer (C.D.C. Cyber-205). Executing the same runs on a serial computer would take a prohibitively long computer time. Details of the vectorization of the phonon programs will be published elsewhere [l5l. 

The self-energy effect in the phonon feature of a superconducting point contact can be used, in principle, in the same way as the Rowell-McMillan program for determination of the EPI spectral function in tunneling spectroscopy of superconductors [16]. Two difficulties arise on this way. One is theoretical, since this program works well only for the one-band superconductor, and its application to the two-band case, like MgB2, encounters difficulties [17]. The other is experimental, since all other sources of I — V nonlinearities should be removed, and especially, the nonequilibrium effects in superconductor should be excluded. 

The general topic of surface analysis has already generated several books and some hundreds of review articles, so it is clearly outside the scope of this chapter to provide a comprehensive discussion of all of the techniques presently available for the study of clean surfaces and adsorption/desorption processes. Instead, we shall consider a few of the methods most relevant to semiconductors which have perhaps been treated less extensively elsewhere. We shall also concentrate on the type of information available rather than the details of its production. In Fig. 1, we have attempted to illustrate the complete range of surface evaluation techniques, from which we see that a surface can be probed by electrons, ions, photons, neutral particles and phonons (temperature programming), and the products of the resulting interactions analysed in various ways. 

The procedure for extracting the phonon DOS from the energy dependence of the probability for nuclear inelastic absorption and calculation of the vibrational thermodynamics has been coded in three programs DOS [110], PHOENIX [III], and INES [I 12]. They are freely available from the authors. 

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