Spin-Peierls transitions in S>1/2 Heisenberg chains

Exact diagonalizations are done to calculate the energy gain from bond alternation in finite spin chains as a function of chain length. Calculations are done for S=1/2, 1, 3/2, and 2. Qualitative differences are found between half-integer and interger spins. Our results (i) indicate the absence of the spin-Peierls transition in systems with integer spins and (ii) suggest a transition in systems with half-integer spins.