摘要:

A continuous random network (CRN), consisting of 238 tetrahedrally co‐ordinated atoms, has been constructed so as to contain only even‐membered rings. Its basic structural properties are reviewed and compared with those of the Polk‐like 201‐atom model of Steinhardt et al. The correlations of bond length and bond angle distortions are investigated and their effect on the structure and its strain energy estimated. Finally, a CRN is proposed that should describe the structure of amorphous Ge more accurately than either of the present models.

ISSN:0094-243X    

DOI:10.1063/1.2945959

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Energy minimization was performed by computer on models of a‐Ge and crystalline GeIIIand GeIV. The force constants obtained by minimizing the lattice energy are shown to vary systematically with density of the structure. This variation removes the discrepancies between the experimental and calculated values of the transformation enthalpies of a‐Ge, GeIIIand GeIV.

ISSN:0094-243X    

DOI:10.1063/1.2945961

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A brief summary of a set of rules for constructing random networks on a computer are given. The structures produced can be constructed to vary systematically with physically meaningful parameters.

ISSN:0094-243X    

DOI:10.1063/1.2945962

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The construction and refinement of cluster and periodic, models useful for understanding the structure, vibrational and electronic properties of amorphous tetrahedrally bonded materials are described. In particular, broadened radial distribution functions of cluster models are shown to accord very well with experiments on amorphous germanium. The anisotropic diffraction properties discovered by Chaudhari and Graczyk are also discussed.

ISSN:0094-243X    

DOI:10.1063/1.2945963

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Deleting the 2‐connected points which represent oxygen atoms in a random network model of vitreous silica yields a model for a 1‐element tetrahedral structure consisting of 651 point‐atoms. The distribution of pair distances gives 5 distinguishable peaks. The first peak is Gaussian and the second peak is nearly so. The details of the asymmetric 3rd peak largely reflect the various geometries of 6‐membered rings. Mathematical manipulation of the atom coordinates can be made such that the areas of the first 2 peaks can be redistributed without breaking any connections or significantly changing the significant details of peaks at larger distances. Coordination or packing numbers for the average atom have been obtained by a topological analysis.

ISSN:0094-243X    

DOI:10.1063/1.2945964

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Examples of quasi‐random networks with perfect 4‐fold coordination bounded by identical copies of themselves can be simulated on a digital computer, starting from an arrangement of the same atoms on a lattice, and stochastically joining each atom to four of a set of its neighbors. After relaxation under a simple valence‐force law, these nets bear an encouraging resemblance to the structure of amorphous germanium. A simple calculation of the vibrational spectrum is also presented.

ISSN:0094-243X    

DOI:10.1063/1.2945965

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A theory is presented in which the radial distribution function (RDF) of an amorphous solid is considered to be the sum of a series of shells of n‐bond neighbors. Application of the theory to the structure of amorphous Ge accounts quantitatively for the experimental RDF out to a radius of 6Å. Limits are placed on the dihedral angle distribution indicating that staggered‐like configurations are more probable than eclipsed‐like.

ISSN:0094-243X    

DOI:10.1063/1.2945966

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Pressure‐induced semiconductor‐metal transitions have been found in amorphous Si, Ge andInSbat about 100, 60 and 12 kbar, respectively. The high‐pressure metallic modifications of Si remain amorphous, while those of Ge andInSbcrystallize into cubic or tetragonal structure. The metallic character has been demonstrated by the superconductivity and the positive magnetoresistance.

ISSN:0094-243X    

DOI:10.1063/1.2945967

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Experiments have been performed in which the angle of arrival of the Ge vapor has been varied from 90° to 45°. Three differences have been noted in the experiments to date: 1) there is a measurable change in the photomission energy distributions (suggesting a corresponding change in electronic structure); 2) the crystallization temperature is increased by over 100° K at 45° incidence and, 3) the 45° films are much more porous than the 90° films as judged from the effect of atmospheric exposure on electrical conductivity.

ISSN:0094-243X    

DOI:10.1063/1.2945968

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In order to determine if any structural effects could be observed accompanying the angle of evaporation effects described at this meeting by Orlowski, Spicer, and Baer, electron diffraction patterns were compared from Ge films that had been evaporated on to parlodion substrates at normal and 45° incidence. It was observed that in all cases the second diffraction peak was weaker with respect to the first peak in the 45° films. This observation indicates that changing the angle of incidence during evaporation could either alter the orientation of some anisotropic structural entity or produce some true structural change.

ISSN:0094-243X    

DOI:10.1063/1.2945969

出版商:AIP    

年代:1974

数据来源: AIP