Molecular Dynamics Simulation of the Adsorption of Oxalic Acid on an Ice Surface

Abstract

The adsorption properties of oxalic acid molecules on the surface of hexagonal ice are investigated by means of molecular dynamics simulations performed at tropospheric temperatures. Although the oxalic acid-water interaction is strong at low coverage, due to the possible formation of a large number of hydrogen bonds between the adsorbed oxalic acid and the surface water molecules, the results of the simulations at finite coverage show the predominant role played by the oxalic acid-oxalic acid lateral interactions in the adsorption/desorption process. These interactions are even stronger than the water-water or water-oxalic acid interactions. With increasing temperature these strong lateral interactions favor the formation of oxalic acid aggregates on the ice surface, with the concomitant departure of water molecules through the ducts in the adsorbed layer created by the aggregation process. These results support conclusions of experimental data on the oxalic acid-ice interactions. Moreover, in comparison to previously obtained results for formic and acetic acid adsorbed on ice, the present study suggests that not only the organic functionality is of importance for atmospheric implications of partially oxidized hydrocarbons (POH) interactions with ice, but also the balance between water-ice, water-POH, and POH-POH interactions.

Water and formic acid aggregates: A molecular dynamics study

“…This is indeed the case for a wide variety of atmospherically relevant organic compounds for which the accuracy of the interaction models with water has been tested in recent years, on the basis of classical molecular dynamics and Monte Carlo simulations aiming at investigating VOC adsorption on, i.e., ice surfaces. [8][9][10][11][12][13][14][15][16][17][18] A few molecular dynamics simulation studies have thus been recently devoted to a detailed investigation of the behavior of large droplets made of water and organic molecules used as surrogates for organic aerosols. Either big water droplets coated by various organic molecules [19][20][21][22][23][24] or the reverse situation, i.e., large organic aggregates interacting with surrounding water molecules 25,26 have been considered in the corresponding theoretical works, as a function of temperature.…”

Analysis of Mixed Formic and Acetic Acid Aggregates Interacting With Water: A Molecular Dynamics Simulation Study

“…Moreover, the use of such a classical approach was based on the confidence given by the successful comparison between the results of previous computer simulations of carboxylic acid molecules on ice and the corresponding experimental conclusions. [19][20][21][22] Thus, the behavior of the three smallest carboxylic (i.e., formic, 16 acetic and propionic 17 ) and the two smallest dicarboxylic (i.e., oxalic, 14 malonic 15 ) acid molecules has been characterized in detail in a broad range of temperatures and for different water:acid ratios.…”

Adsorption of Methylamine at the Surface of Ice. A Grand Canonical Monte Carlo Simulation Study

“…[23][24][25][26][27][28][29][30][31][32] In addition, Grand Canonical Monte Carlo (GCMC) simulations 17,33 have also been performed to simulate the adsorption isotherms of various classes of volatile organic compounds and atmospheric pollutants on ice at low temperatures. [34][35][36][37][38][39][40][41][42][43][44] Indeed, the GCMC method is particularly suitable for studying adsorption, because in this method the chemical potential rather than the number of the adsorbate molecules is fixed in the simulation.…”