  We report a real-space renormalization group (RSRG) algorithm, which is
formulated through Baxter's corner transfer matrix (CTM), for two-dimensional
(d = 2) classical lattice models. The new method performs the renormalization
group transformation according to White's density matrix algorithm, so that
variational free energies are minimized within a restricted degree of freedom
m. As a consequence of the renormalization, spin variables on each corner of
CTM are replaced by a m-state block spin variable. It is shown that the
thermodynamic functions and critical exponents of the q = 2, 3 Potts models can
be precisely evaluated by use of the renormalization group method.
