NMR chemical shifts as a tool to analyze first principles molecular dynamics simulations in condensed phases: the case of liquid water

Abstract

We present (1)H NMR chemical shift calculations of liquid water based on first principles molecular dynamics simulations under periodic boundary conditions. We focus on the impact of computational parameters on the structural and spectroscopic data, which is an important question for understanding how sensitive the computed (1)H NMR resonances are upon variation of the simulation setup. In particular, we discuss the influence of the exchange-correlation functional and the size of the basis set, the choice for the fictitious electronic mass and the use of pseudopotentials for the nuclear magnetic resonance (NMR) calculation on one hand and the underlying Car-Parrinello-type molecular dynamics simulations on the other hand. Our findings show that the direct effect of these parameters on (1)H shifts is not big, whereas the indirect dependence via the structural data is more important. The (1)H NMR chemical shifts clearly reflect the induced structural changes, illustrating once again the sensitivity of (1)H NMR observables on small changes in the local chemical structure of complex hydrogen-bonded liquids.

Six-site polarizable model of water based on the classical Drude oscillator

“…The approach developed by Sebastiani and Parrinello, 66 which was shown to give good estimation of NMR shifts, 67 was used. Similar to the procedures adopted by Banyai et al, 68 30 structures were extracted from a NPT MD trajectory of a system of 32 water molecules and the nuclear magnetic shieldings were calculated with the BLYP method 69,70 and the Goedecker type pseudopotentials 71 for the two hydrogen atoms in all water molecules, using the NMR module implemented in the CPMD program. 72 This results in 2 × 32 × 30 = 1920 data points for which the average was evaluated to represent the final nuclear magnetic shielding of the water hydrogens for the SWM6 model.…”

“…The good performance of SWM6 in reproducing the experimental g OO (r) suggests that the local water structure in bulk phase is better reproduced with the new model. To further characterize properties related to the local water structure, NMR shielding, and the related chemical shifts, which are sensitive indictors of the local hydrogen bonding structure, were calculated following the protocol used by Banyai et al 68 It was shown that the applied density functional method based protocol can give chemical shifts that are close to the experimental value for the bulk water structures collected from ab initio MD simulations. 68 The results are shown in Table IV 99 However, with the same simulation setups as used by Banyai et al, 68 it can be concluded that the SWM6 model yields local hydrogen bonding structures that are closer to the ab initio MD structures when compared to the other tested models.…”

Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies

“…Therefore, various physical effects such as van der Waals interactions between molecules and the quantum behaviour of nuclei have to been reproduced only approximately or even completely neglected. In addition, the high computational cost of AIMD imposes severe restrictions on the size of a model system and time length of the simulations thus introducing additional finite-size errors and statistical uncertainties into the properties calculated [99][100][101][102][103][104][105][106][107] .…”

Ab Initio H2O in Realistic Hydrophilic Confinement

“…The self-consistent field (SCF) convergence was set to 6 10 À7 a.u. [32][33][34] We used the deuteron mass for the hydrogen atoms and a time step of 1 fs. The system was thermostatically controlled to 350 K by using a CSVR thermostat [31] with a time constant of 100 fs.…”