Nonrelativistic molecular quantum mechanics without approximations: Electron affinities of LiH and LiD

Abstract

We took the complete nonrelativistic Hamiltonians for the LiH and LiH Ϫ systems, as well as their deuterated isotopomers, we separated the kinetic energy of the center of mass motion from the Hamiltonians, and with the use of the variational method we optimized the ground-state nonadiabatic wave functions for the systems expanding them in terms of n-particle explicitly correlated Gaussian functions. With 3600 functions in the expansions we obtained the lowest ever ground-state energies of LiH, LiD, LiH Ϫ , and LiD Ϫ and these values were used to determine LiH and LiD electrons affinities ͑EAs͒ yielding 0.330 30 and 0.327 13 eV, respectively. The present are the first high-accuracy ab initio quantum mechanical calculations of the LiH and LiD EAs that do not assume the Born-Oppenheimer approximation. The obtained EAs fall within the uncertainty brackets of the experimental results.

Electronic structure and time-dependent description of rotational predissociation of LiH

“…Gadea and coworkers calculated potential energy curves 2,6,7,8 , radial couplings 9 , nonaa Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, Naru-diabatic energy shifts 10 as well as the LiH formation by radiative association in ion collisions 11 . Results of several other calculations, including semiempirical and ab initio approaches to describe important physical and chemical properties of LiH are available 12,13,14,15,16,17,18,19,20,21,22 . Calculations related to LiH are also used in the description of ultracold polar molecules formation in a single quantum state (e.g.…”

Matrix elements of N-particle explicitly correlated Gaussian basis functions with complex exponential parameters

“…4,5 This works quite well in the case of diatomic systems. [6][7][8][9][10][11][12] However, the generalization of this approach to triatomic systems encounters serious problems in obtaining compact analytical expressions for matrix elements and not less serious problems in practical implementation. 13 In this work we consider yet another way of describing the radial nodes in the ground and excited state wave functions of atomic and molecular systems calculated without the use of the Born-Oppenheimer approximation.…”

Vibrational transitions of the $^7$7LiH$^+$+ ion calculated without the Born–Oppenheimer approximation and with leading relativistic corrections

“…Pure vibrational transitions of a three-electron 7 LiH + ion are still unknown experimentally even though it can be readily produced in experimental conditions by a photoinduced electron detachment. This makes the theoretical calculations of pure vibrational transitions an important prerequisite to any attempt to measure them.…”

“…This makes the theoretical calculations of pure vibrational transitions an important prerequisite to any attempt to measure them. In a paper published four years ago 1 we described calculations of six pure vibrational states of 7 LiH + performed at the nonrelativistic level without assuming the Born-Oppenheimer (BO) approximation. In the calculations we employed explicitly correlated Gaussian basis functions multipled by powers of the internuclear distance.…”

“…For 3 He 4 He + the calculations reproduced within 0.06 cm −1 the fundamental vibrational transition, which is known with very high accuracy of about 0.001 cm −1 . 3 In that work we also calculated the fundamental transition of 7 LiH + . As the approach used in the 7 LiH + calculations was the same as used for 3 He 4 He + , a similar accuracy was claimed for the 7 LiH + transition.…”