We present results of a density functional theory study of the structu
re and energetics of small Pt clusters. The method of calculation is b
ased on the non-selfconsistent Harris functional version of LDA (as fo
rmulated by Sankey and Niklewski, and generalized to include d orbital
s in the basis set), which produces excellent results for bulk Pt. We
used a dynamical quenching algorithm to obtain minimum-energy structur
es of Pt-n clusters for n = 2-6. The clusters with n = 4-6 are shown t
o be planar. For Pt-13 we found that there is a variety of low-symmetr
y geometries that are lower in energy than the icosahedral and cube-oc
tahedral structures. We also compute the vibrational states of n = 2-4
, and show that the calculated vibrational frequency and bond energy o
f the Pt dimer are in good agreement with experiments.