Analytical energy gradient in variational calculations of the two lowest P-3 states of the carbon atom with explicitly correlated Gaussian basis functions

作者：Sharkey Keeper L^*; Bubin Sergiy; Adamowicz Ludwik

来源：Journal of Chemical Physics, 2010, 132(18): 184106.

DOI：10.1063/1.3419931

• bound states
• carbon
• excited states
• Gaussian distribution
• ground states
• variational techniques

Variational calculations of ground and excited bound states on atomic and molecular systems performed with basis functions that explicitly depend on the interparticle distances can generate very accurate results provided that the basis function parameters are thoroughly optimized by the minimization of the energy. In this work we have derived the algorithm for the gradient of the energy determined with respect to the nonlinear exponential parameters of explicitly correlated Gaussian functions used in calculating n-electron atomic systems with two p-electrons and (n-2) s-electrons. The atomic Hamiltonian we used was obtained by rigorously separating out the kinetic energy of the center of mass motion from the laboratory-frame Hamiltonian and explicitly depends on the finite mass of the nucleus. The advantage of having the gradient available in the variational minimization of the energy is demonstrated in the calculations of the ground and the first excited P-3 state of the carbon atom. For the former the lowest energy upper bound ever obtained is reported.

• 出版日期2010-5-14