The energetics and the structural stability of lanthanum microclusters (La-n) have been investigated by performing relativistic density functional calculations and molecular dynamics (MD) simulations. An empirical potential energy function has been parameterised for a lanthanum element by using the dimer interaction potential energy profile of La-2, which is calculated by relativistic density functional method. Stable structures of the microclusters for n = 3-13 have been determined by MD simulation and electronic structures have been calculated by relativistic density functional method. MD simulations have also been performed for spherical clusters with sizes n = 19-157. (C) 1999 Elsevier Science B.V. All rights reserved.