Band structure of the one-dimensional metallic (SN)x crystal

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Abstract
A self‐consistent LCAO tight binding calculation of the band structure of the one‐dimensional (SN)x crystal is performed. Convergence of the band structure as a function of the interaction range and the number of translational irreducible representations that are allowed to interact (via the Hartree–Fock elements) as well as the SCF iteration cycle convergence are examined. The crystal is shown to possess a partially occupied valence band in accord with its experimentally established metallic behavior. Bond alternancy is investigated by examining the stability of the total energy with respect to conformational changes. The alternant structure is shown to be more stable than the equal‐bond structure. Analysis of the charge distribution in the system reveals a low ionicity of the S+δN−δ bond (δ=0.18e) and points to the possibitlity of formation of cross bonds between nonbonded S–S pairs. The possibility of the occurrence of a Peierls instability was investigated by searching for a superlattice of model conformational distortions in the (SN)x chain that will both produce a gap around the Fermi level and lower the total Hartree–Fock crystal energy. Such an instability was not found, and the crystal was shown to behave like a metal for all the conformations studied.

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