COMPUTATION OF STRUCTURE AND ENERGY OF THE Σ3 (21(-1)) TILT BOUNDARY IN SILICON M. CHEIKH, A. HAIRIE, F. HAIRIE, G. NOUET and E. PAUMIER J. Phys. Colloques, 51 C1 (1990) C1-103-C1-108 DOI: 10.1051/jphyscol:1990114