TY - JOUR

T1 - Relaxed continuous random network models. (I). Structural characteristics

AU - Steinhardt, P.

AU - Alben, R.

AU - Weaire, D.

N1 - Funding Information:
The reasonableness of the continuous random network (CNR) model for the structure of tetrahedraUy coordinated amorphous semiconductors is demonstrated by Polk \[1 \], who showed that it is possible to connect rather rigid plastic and metal tetrahedral molecular units in a structure with little bond strain, no unsatisfied bonds and no perceptible long-range order \[1-3\]. For several years, our knowledge of the characteristics of these structures was based on laborious direct measurements of a single model of 440 units built by Polk \[1 \]. Models built by computer methods \[4, *Research supported in part by NSF. **Presenta ddress: Dept. of Physics, California Institute of Technology, Pasadena, California 91109.

PY - 1974/6

Y1 - 1974/6

N2 - Two elastic-energy-relaxed continuous random network (Polk) models for tetrahedrally bonded amorphous semiconductors have been obtained: a 201-atom model built entirely at Yale and a 519-atom model relaxed from a structure built by Polk and Boudreaux which originated at Harvard. In relaxing the coordinates to minimize the total energy the Keating potential was used for the interatomic interactions. The models are analyzed in terms of density, elastic distortion energy, elastic constants, numbers of five-, six- and seven-fold rings, distribution of dihedral angles, and radial distribution functions. We find that, despite their different origins, the models have essentially identical characteristics. Our principal conclusions are as follows: (a) The density of the CRN model is, to within 1%, that of diamond cubic. (b) The bulk modulus is about 3% lower than that for the diamond cubic structure and the shear modulus lies between the two diamond cubic shear moduli. (c) There are, to within ± 10% (and with corrections for surface effects), 0.38 five-fold, 0.91 six-fold and 1.04 seven-fold rings per atom. (d) For a reasonable value of the bond bending force constant, rms bond length distortions are about 1.0% and bond angle distortions are about 7.0°. (e) The radial distribution function agrees very well with experiment for all four principal peaks.

AB - Two elastic-energy-relaxed continuous random network (Polk) models for tetrahedrally bonded amorphous semiconductors have been obtained: a 201-atom model built entirely at Yale and a 519-atom model relaxed from a structure built by Polk and Boudreaux which originated at Harvard. In relaxing the coordinates to minimize the total energy the Keating potential was used for the interatomic interactions. The models are analyzed in terms of density, elastic distortion energy, elastic constants, numbers of five-, six- and seven-fold rings, distribution of dihedral angles, and radial distribution functions. We find that, despite their different origins, the models have essentially identical characteristics. Our principal conclusions are as follows: (a) The density of the CRN model is, to within 1%, that of diamond cubic. (b) The bulk modulus is about 3% lower than that for the diamond cubic structure and the shear modulus lies between the two diamond cubic shear moduli. (c) There are, to within ± 10% (and with corrections for surface effects), 0.38 five-fold, 0.91 six-fold and 1.04 seven-fold rings per atom. (d) For a reasonable value of the bond bending force constant, rms bond length distortions are about 1.0% and bond angle distortions are about 7.0°. (e) The radial distribution function agrees very well with experiment for all four principal peaks.

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U2 - 10.1016/0022-3093(74)90049-0

DO - 10.1016/0022-3093(74)90049-0

M3 - Article

AN - SCOPUS:0016071915

VL - 15

SP - 199

EP - 214

JO - Journal of Non-Crystalline Solids

JF - Journal of Non-Crystalline Solids

SN - 0022-3093

IS - 2

ER -