  An algorithm is proposed to optimize quantum Monte Carlo (QMC) wave functions
based on New ton's method and analytical computation of the first and second
derivatives of the variati onal energy. This direct application of the
variational principle yields significantly low er energy than variance
minimization methods when applied to the same trial wave function.
  Quadratic convergence to the local minimum of the variational parameters is
achieved. A g eneral theorem is presented, which substantially simplifies the
analytic expressions of de rivatives in the case of wave function optimization.
To demonstrate the method, the ground state energies of the first-row elements
are calculated.
