Configuration interaction calculations of annihilation rates for positronic complexes of alkali hydrides

摘要: Abstract Ab initio multireference single- and double-excitation configuration interaction (MRD-CI) wave functions have been employed to compute the annihilation rates (AR) of positronic molecular complexes four alkali hydrides. The first step in these calculations is evaluation integrals two-particle Dirac delta function δ+− over pairs electronic basis functions. MRD-CI calculated with same are then obtain expectation values operator (Zeff), which turn proportional corresponding associated many-particle states. importance removing near-linear dependencies sets stressed as well advisability placing diffuse (small-exponent) only at most electronegative center molecule. A tendency underestimate Zeff noted because impracticality including sufficiently high-l for general systems. However, comparison relatively accurate four-electron e+LiH complex obtained by Quantum Monte-Carlo (QMC) other methods indicates that fractional error nearly constant a large range internuclear distance, consistent missing correlation effects treatment predominantly atomic nature. scaling procedure based on asymptotic value, all hydrides, shown produce good agreement QMC AR data e+LiH. has applied heavier hydrides no theoretical results available. Trends variation bond distance discussed.