We have calculated a new stable structure and the electronic structure of boron clusters in silicon crystal. According to our calculation, which was based on the first-principles local density functional approach forSi54B12H60clusters, the cubo-octahedralB12cluster was found to be more stable than the icosahedral one proposed previously. The total energy difference was about 4.6 eV. The analysis of the partial density of states showed that the cubo-octahedralB12cluster should act as a double acceptor. ©1997 American Institute of Physics.