Diffusion and Reptation Quantum Monte Carlo Study of the NaK Molecule

24 August 2018, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Diffusion Monte Carlo (DMC) and Reptation Monte Carlo (RMC) methods, have been applied to study some properties of the NaK molecule. Hartree-Fock (HF), Density Functional (DFT) and single and double configuration interaction (SDCI) wavefunctions with a valence quadruple zeta atomic natural orbital (VQZ/ANO) basis set were used as trial wavefunctions. Values for the potential energy curve, dissociation energy and dipole moment were calculated for all methods and compared with experimental results and previous theoretical derivations. Quantum Monte Carlo (QMC) calculations were shown to be useful methods to recover correlation in NaK, essential to obtain a reasonable description of the molecule. The equilibrium distance—interpolated from the potential energy curves—yield a value of 3.5 Å, in agreement with the experimental value. The dissociation energy, however, is not as good. In this case, a conventional CCSD(T) calculation with an extended aug-pc-4 basis set gives a much better agreement to experiment. On the contrary, the CCSD(T), other MO and DFT methods are not able to reproduce correctly the large dipole moment of this molecule. Even DMC methods with a simple HF trial wavefunction are able to give a better agreement to experiment. RMC methods are even better, and the value obtained with a B3LYP trial wavefunction is very close to the experimental one.

Keywords

quantum monte carlo
NaK
density functional methods
dipole moment

Supplementary materials

Title
Description
Actions
Title
Diffusion and reptation quantum Monte Carlo study of the NaK molecule 2
Description
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.