The dangling-bond concept of bare surfaces of covalent crystals is reconsidered in terms of molecular magnetism of highspin free radicals with the relevant spin multiplicity (SM) [(Nα - Nβ) + 1], where Nα - Nβ determines the number of unpaired electrons of the surface unit cell. The electronic structure of the (1 1 1)(7 × 7) and (0 0 1)(2 × 1) surfaces has been studied at different SMs. For both surfaces, highspin states are energetically favorable. Spin density distribution is discussed in view of particular magnetic behavior of the surfaces. © 2003 Elsevier Science B.V. All rights reserved.