Algebraic Representation of Many-Particle Coulomb Green Function and   Application in Atomic Calculations
  Basing on the relation between the Coulomb Green function and the Green function of harmonic oscillator, the algebraic representation of the many-particle Coulomb Green function in the form of annihilation and creation operators is established. These results allow us to construct purely algebraic method for atomic calculations and thus to reduce rather complicated calculations of matrix elements to algebraic procedures of transforming the products of annihilation and creation operators to a normal form. Effectiveness of the constructed method is demonstrated through the example problem: the ground state of hydrogenic molecule. The calculation algorithm of this algebraic approach is simple and suitable for symbolic calculation programs, such as Mathematica, that widely enlarge the application field of the Coulomb Green function 
Nguyen Hoang Quoc, Nguyen Ngoc Ty, Le Van Hoang, Nguyen Khac Nhap