Carbon dioxide in aqueous environment—A quantum mechanical charge field molecular dynamics study

Abstract

Structure and dynamics of a carbon dioxide molecule in water were studied by an ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) simulation. Radial distribution functions, angular distribution functions, and coordination number distributions as well as dynamical data such as mean ligand residence time and vibrational spectra were utilized for the evaluation of physico-chemical properties of hydrated CO 2 . These data served for an assessment of hydrogen bonding between solute and solvent molecules. All the results evaluated were compared with available experimental results leading to a good agreement between theoretical and experimental data. The average lifetime of hydrogen bonding between H 2 O and CO 2 resulted as 0.61 ps, which is higher than the hydrogen bonding lifetime of pure water. The vibrational frequencies were also calculated for all the modes of hydrated CO 2 to demonstrate the influence of solvent molecules on the IR spectrum of the solute.

Molecular Simulation Models of Carbon Dioxide Intercalation in Hydrated Sodium Montmorillonite

“…The frequency of the CO2 asymmetric stretch is calculated to occur 8 cm -1 to the red from the fundamental vibration of the gas-phase CO2 molecule (Figure 9). This is consistent with the peak in the experimental band of the asymmetric stretch showing a red shift about 6 cm -1 relative to the gas-phase molecule (Garrett-Roe et al, 2009;Moin et al, 2011).…”

“…This also suggests that in the reported experiments (Loring et al, 2012;Romanov et al, 2010a,b;Romanov, 2013) hydration of CO2 in the interlayer space is sufficient to form a solvation shell and preclude a direct interaction of CO2 with sodium cations, which would act so as to cause a blue-shift (Gregoire and Duncan, 2002;Walker et al, 2003;Jaeger et al, 2004). Remarkably, a similar red shift in the stretch fundamental was found by Moin et al (2011), in their mixed ab initio/force field MD simulations of carbon dioxide in water. Figure 11: Correlation between a red shift of the asymmetric stretch vibration and a corresponding sum of incremental deviation of the bond lengths (L1+L2) for the CO2 monomer relative to the gas-phase value.…”

The hydration structure of dissolved carbon dioxide from X-ray absorption spectroscopy

“…The chemical reaction of CO 2 with water to form carbonic acid is clearly the central feature of these carbonate equilibria, and has been addressed by many experiments [5,16,[18][19][20][21][22][23][24][25][26] and calculations [17,[27][28][29][30][31][32][33][34][35][36] with conflicting results. Details of the neutral CO 2 solvation by bulk water prepare the reaction pathway, and are thus a determining factor in this chemistry.…”

CO2concentration and pH alters subsurface microbial ecology at reservoir temperature and pressure

“…13 In aqueous systems with a high pCO 2 exposure, the pH may be as low as $3.5 to 4.5, 3 and much of the dissolved CO 2 is in the form of CO 2(aq) rather than a carbonic acid. 14,15 This small, nonpolar molecule may then diffuse through cell membranes, disrupting cell growth by changing the cell uidity, inhibiting intercellular enzyme performance, and affecting the intercellular pH. 11 However, while laboratory cultures have been found to decrease cell viability with CO 2 exposure, 10,11,13,16,17 other studies suggest native subsurface species may be adaptable to CO 2 environments.…”