Spectroscopic accuracy directly from quantum chemistry: Application to ground and excited states of beryllium dimer

{We combine explicit correlation via the canonical transcorrelation approach with the density matrix renormalization group and initiator full configuration interaction quantum Monte Carlo methods to compute a near-exact beryllium dimer curve, without the use of composite methods. In particular, our direct density matrix renormalization group calculations produce a well-depth of D-e = 931.2 cm(-1) which agrees very well with recent experimentally derived estimates D-e = 929.7 +/- 2 cm(-1) {[}J. M. Merritt, V. E. Bondybey, and M. C. Heaven, Science 324, 1548 (2009)] and D-e = 934.6 cm(-1) {[}K. Patkowski, V. Spirko, and K. Szalewicz, Science 326, 1382 (2009)], as well the best composite theoretical estimates