Ab initio molecular-dynamics studies on SrN (N = 2–35, 55 and 147) clusters show d electron induced icosahedral growth. There is a gradual increase in the hybridization between the sp and d states as well as the metallization of clusters as the size grows. For Sr147, the highest occupied and lowest unoccupied molecular orbital gap becomes vanishingly small. The nonmetal-metal transition is found to occur more prominently along the close-packed directions from the center to the 12 vertices with an oscillatory behavior of the bond length. However, in other directions, there is a monotonic expansion as one goes from the center to the surface of the cluster. This is in contrast to contraction known in other metal clusters but agrees with the interlayer expansion found on the surfaces of divalent metals. {\textcopyright} 2001 The American Physical Society.