Quantum simulation for muoniated and deuterated methyl radicals in implicit water solvent: combined ab initio path integral molecular dynamics and the polarizable continuum model simulation study

Abstract

We have combined ab initio path integral molecular dynamics (PIMD) simulation and the polarizable continuum model (PCM) method to efficiently incorporate solvent effects into nuclear quantum fluctuation of molecular systems. Our combined ab initio PIMD–PCM simulation was applied to muoniated and deuterated methyl radical immersed in implicit water solvent to gain information on solvent and isotope effects from one simulation run. We found that solvent effects lead to the bond elongation and a decrease in the magnitude of isotropic hyperfine coupling constants. These are consistent with the trends in conventional static calculations and experiments. In addition, the performance of cavity models (universal force field, united atom specified for Kohn–Sham and these hybrid models) and the conservation of the PIMD–PCM Hamiltonian were accessed. We confirmed that solvent effects on nuclear quantum fluctuation are efficiently computed using our combined simulation of quantum solute in implicit solvent.

Keywords::

• ab initio path integral molecular dynamics simulation
• polarizable continuum model method
• solvent effects
• muonium
• isotope effect

Acknowledgements

Financial support was provided by Grant-in-Aid for Scientific Research and for the priority area by the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Notes

^1. The cavity models may be dependent on program suite used in simulation.

^2. The hybrid model was performed using ‘scrf = (cpcm, read)’ with ‘nsph = 2’ and its arguments ‘1 2.130 1.00’ and ‘2 1.443 1.00’. Note that the first and second atoms correspond to the C and Mu atoms, respectively. In addition, in this paper, scale factor for atom-centred radii was set to 1.0, while its defalut value is 1.1.

^3. A planar configuration is the optimised structure in the gas phase at the O3LYP/6-311G(d,p) level of theory, and pyramidal configuration is the structure where all structural parameters are the same as those of the planar configuration except for the dihedral angle of 83.9°.