Modified adiabatic approximation: charge asymmetry in HD+ and HD

Area of Science:

• Quantum chemistry
• Molecular physics
• Computational chemistry

Background:

• Accurate molecular simulations require accounting for the finite mass of atomic nuclei.
• Traditional methods often neglect or approximate these nuclear effects, limiting precision.
• Understanding nuclear motion is crucial for interpreting molecular spectra and properties.

Purpose of the Study:

• To develop a universal computational method that incorporates finite nuclear mass effects.
• To improve the simulation of electron-nucleus interactions in molecular systems.
• To validate the new method by reproducing known phenomena in hydrogen deuteride.

Main Methods:

• A modified adiabatic approximation is proposed, partitioning electron-nucleus interactions between electronic and nuclear Hamiltonians.
• The formalism is designed to be applicable to molecules of any size.
• The method was tested on vibrationally excited states of HD(+) and the permanent dipole moment of HD.

Main Results:

• The modified adiabatic approximation successfully simulates the finite nuclear mass effect.
• Electron localization on the deuteron in HD(+) was accurately reproduced.
• The permanent dipole moment of HD was well reproduced, matching experimental and theoretical expectations.

Conclusions:

• The proposed modified adiabatic approximation offers a universal and accurate approach for molecular calculations.
• This method provides a more rigorous treatment of nuclear quantum effects.
• It enhances the ability to predict and explain molecular properties influenced by nuclear motion.