  Thermodynamic properties of the one-dimensional Kondo lattice model at
half-filling are studied by the density matrix renormalization group method
applied to the quantum transfer matrix. Spin susceptibility, charge
susceptibility, and specific heat are calculated down to T=0.1t for various
exchange constants. The obtained results clearly show crossover behavior from
the high temperature regime of nearly independent localized spins and
conduction electrons to the low temperature regime where the two degrees of
freedom couple strongly. The low temperature energy scales of the charge and
spin susceptibilities are determined and shown to be equal to the quasiparticle
gap and the spin gap, respectively, for weak exchange couplings.
