Positron chemistry by quantum Monte Carlo. II. Ground-state of positron-polar molecule complexes

Abstract

The stability of the ground-state of positron-polar molecule complexes ͓M,e ϩ ͔ has been explored for MϭLiH,HF,H 2 O,BeO,LiF using variational and diffusion Monte Carlo techniques. Our simulations show that the ground-state of the complexes ͓LiH,e ϩ ͔ 2,1 ⌺ ϩ , ͓BeO,e ϩ ͔ 2,1 ⌺ ϩ , and ͓LiF,e ϩ ͔ 2,1 ⌺ ϩ is stable against the dissociation either in the two fragments M and e ϩ or in the other two fragments M ϩ and Psϭ͓e ϩ ,e Ϫ ͔, while the ground-state of ͓H 2 O,e ϩ ͔ 2,1 A 1 , and of ͓HF,e ϩ ͔ 2,1 ⌺ ϩ has an energy equal to the dissociation threshold, M and e ϩ. We also compare the predicted vertical positron affinity ͑PA͒ with high quality vertical electron affinity ͑EA͒ and discuss the relevant difference between the two values.

Annihilation rate in positronic systems by quantum Monte Carlo: e+LiH as test case

“…We notice that a similar behavior of δ(r −+ ) may be expected also for e + LiF due to the polarization of the positronic density of the PsF fragment by the Li + core. The situation could be quite different for the e + BeO case where the positron density is expected to be centered on Be at large nuclear distances (the two fragments e + Be and O have lower total energy than Be + and PsO [39]), and to move on the O side of the molecule when the distance decreases. This effect is due to the electron transfer from Be to O that creates the large molecular dipole moment.…”

Full-correlation single-particle positron potentials for a positron and positronium interacting with atoms

“…The many-body wave functions of small positronic systems composed by a positron interacting with a light atom or a small molecule can be calculated to a good accuracy using the quantum Monte Carlo (QMC) [11][12][13][14][15][16] and configurationinteraction (CI) [17] methods. In this work, we have obtained accurate positron energies and densities for positronic atoms including a positron (e + H, e + He, e + Li, and e + Be) and Ps (HPs and LiPs) by an exact diagonalization stochastic variational method (SVM) using an explicitly correlated Gaussian (ECG) function basis set.…”

Theoretical Study of Positronic Atoms with Adiabatic Separation of Positronic Motion

“…In such situation, establishing the energetic stability of AB requires explicit calculation of D 0 with Eq. (10).…”

“…Further calculations on various positronic atoms quickly followed (see [3] for a review and [4][5][6][7][8] for more recent results). Besides of variational calculations with ECG functions, diffusion quantum Monte Carlo simulations appeared to be able to provide accurate energies for positronic systems [9][10][11][12][13]. Unfortunately, the computational cost of both methods increases quickly with the number of active electrons, limiting in practice their applicability to rather small atoms and molecules.…”