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

Szentirmai, Veronika; Szőri, Milán; Picaud, Sylvain; Jedlovszky, Pál

doi:10.1021/acs.jpcc.6b05863

Cited by 12 publications

(60 citation statements)

References 63 publications

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“…Since the surface of the amorphous ice phase, unlike that of crystalline ice, is corrugated, on the molecular length scale, by capillary waves, the adsorbed formamide molecules that belong to the first molecular layer (i.e., that are in direct contact with the amorphous ice phase) cannot be identified as simply as in the case of crystalline ice. Thus, while in the latter case the first adsorbed molecular layer is conventionally defined through the first minimum of the adsorbate density profile, 26,[61][62][63][64][65][66][67][68][69] at the surface of amorphous ice these molecules have to be identified by means of an appropriate intrinsic surface analyzing method. Several such methods have been proposed in the past 15 years, [100][101][102][103][104][105][106] among which the Identification of the Truly Interfacial Molecules (ITIM) 103 turned out to be an excellent compromise between accuracy and computational cost.…”

Section: Identification Of the First Layer Adsorbed Moleculesmentioning

confidence: 99%

Adsorption of Formamide at the Surface of Amorphous and Crystalline Ices under Interstellar and Tropospheric Conditions. A Grand Canonical Monte Carlo Simulation Study

et al. 2019

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The adsorption of formamide is studied both at the surface of crystalline (Ih) ice at 200 K and at the surface of low density amorphous (LDA) ice in the temperature range of 50-200 K by grand canonical Monte Carlo (GCMC) simulation. These systems are characteristic to the upper troposphere and to the interstellar medium (ISM), respectively. Our results reveal that, while no considerable amount of formamide is dissolved in the bulk ice phase in any case, the adsorption of formamide at the ice surface under these conditions is a very strongly preferred process, which has to be taken into account when studying the chemical reactivity in these environments. The adsorption is found to lead to the formation of multimolecular adsorption layer, the occurrence of which somewhat precedes the saturation of the first molecular layer. Due to the strong lateral interaction acting between the adsorbed formamide molecules, the adsorption isotherm does not follow the Langmuir shape.Adsorption is found to be slightly stronger on LDA than Ih ice under identical thermodynamic conditions, due to the larger surface area exposed to the adsorption. Indeed, the monomolecular adsorption capacity of the LDA and Ih ice surfaces is found to be 10.5 ± 0.7 mol/m 2 and 9.4 mol/m 2 , respectively. The first layer formamide molecules are very strongly bound to the ice surface, forming typically four hydrogen bonds with each other and the surface water molecules. The heat of adsorption at infinitely low surface coverage is found to be -105.6 kJ/mol on Ih ice at 200 K.3

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Section: Identification Of the First Layer Adsorbed Moleculesmentioning

confidence: 99%

Adsorption of Formamide at the Surface of Amorphous and Crystalline Ices under Interstellar and Tropospheric Conditions. A Grand Canonical Monte Carlo Simulation Study

et al. 2019

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“…For comparison with our earlier results, at 200 K dumping of configurations has also been done at two more chemical potential values, at which detailed analysis of the adsorption layer on Ih ice was earlier performed. 47 Finally, for reference purposes, configurations have also been saved for analyses at a  value corresponding to the condensed phase of methylamine at 200 K.…”

Section: Grand Canonical Monte Carlomentioning

confidence: 99%

“…23 Among the various computer simulation techniques, the grand canonical Monte Carlo (GCMC) method 23,24 is particularly suitable for studying adsorption, since here the chemical potential rather than the number of the adsorbate molecules in the basic box is fixed, and thus, by systematically varying the chemical potential and determining the number of adsorbate molecules in a set of simulations, the adsorption isotherm can be determined, and simulation results can be analyzed in detail at surface coverage values that are relevant for the given adsorption process. The GCMC method has been successfully applied in the past two decades for a set of systems, such as for the adsorption of various small molecules at carbonaceous surfaces, [25][26][27][28][29][30][31] metal oxides, [32][33][34][35] covalent organic frameworks, [36][37][38] crystalline ice, [39][40][41][42][43][44][45][46][47][48] water clathrates, 49 kaolinite, 50,51 zeolites, [52][53][54][55][56][57][58] self-assembled monolayers, 59,60 and protein crystals. 61 Since icy surfaces in the interstellar medium are predominantly covered by low density amorphous ice (LDA), 18,19 here we study the adsorption of methylamine at the surfac...…”

Section: Introductionmentioning

confidence: 99%

“…The interaction and geometry parameters of the potential models used are collected in Tables 2 and 3 The simulations have been performed using the program MMC 69 in the same way as described in our earlier paper. 47 Thus, in every Monte Carlo step either, by 50% probability, a randomly chosen molecule has been randomly translated by no more than 0.25 Å and randomly rotated by no more than 15 o , or by 50% probability, the number of the methylamine molecules in the basic box has been attempted to be changed by inserting or removing a molecule. Water and methylamine molecules have been selected for particle displacement steps with equal probabilities, and methylamine insertions and deletions have also been performed with 50%-50% probabilities.…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of Methylamine on Amorphous Ice under Interstellar Conditions. A Grand Canonical Monte Carlo Simulation Study

et al. 2018

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The adsorption of methylamine at the surface of amorphous ice is studied at various temperatures, ranging from 20 to 200 K, by grand canonical Monte Carlo simulations under conditions that are characteristic to the interstellar medium (ISM). The results are also compared with those obtained earlier on crystalline ( I) ice. We found that methylamine has a strong ability of being adsorbed on amorphous ice, involving also multilayer adsorption. The decrease of the temperature leads to a substantial increase of this adsorption ability; thus, considerable adsorption is seen at 20-50 K even at bulk gas phase concentrations that are comparable with that of the ISM. Further, methylamine molecules can also be dissolved in the bulk amorphous ice phase. Both the adsorption capacity of amorphous ice and the strength of the adsorption on it are found to be clearly larger than those corresponding to crystalline ( I) ice, due to the molecular scale roughness of the amorphous ice surface as well as to the lack of clear orientational preferences of the water molecules at this surface. Thus, the surface density of the saturated adsorption monolayer is estimated to be 12.6 ± 0.4 μmol/m, 20% larger than the value of 10.35 μmol/m, obtained earlier for I ice, and at low enough surface coverages the adsorbed methylamine molecules are found to easily form up to three hydrogen bonds with the surface water molecules. The estimated heat of adsorption at infinitely low surface coverage is calculated to be -69 ± 5 kJ/mol, being rather close to the estimated heat of solvation in the bulk amorphous ice phase of -74 ± 7 kJ/mol, indicating that there are at least a few positions at the surface where the adsorbed methylamine molecules experience a bulk-like local environment.

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“…Recently we studied the adsorption of methylamine at the surface of both crystalline [22] and amorphous [23] ice from the vapour phase. In these studies we demonstrated the strong tendency of methylamine molecules for being adsorbed at icy surfaces, including their ability even for multilayer adsorption, and characterized the surface orientation of the adsorbed molecules as well as their hydrogen bonding with the surface waters [22,23]. Hoehn et al investigated the energetic and structural properties of a single methylamine molecule at air/water interface [24].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the liquid-vapour interface of aqueous methylamine solutions by computer simulation methods

Horváth

Fábián

Szőri

et al. 2019

Journal of Molecular Liquids

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Molecular dynamics simulations of the liquid-vapour interface of water-methylamine mixtures of eight different compositions, including neat water, are performed on the canonical (N,V,T) ensemble at 280 K. The molecules constituting the first three individual molecular layers beneath the liquid surface are identified by the Identification of the Truly Interfacial Molecules (ITIM) method. The results indicate that methylamine molecules are strongly adsorbed in the first, and somewhat depleted in the second molecular layer, while the composition of the third layer agrees well with that of the bulk liquid phase. On the other hand, methylamine molecules do not show considerable self-association within the surface layer. The orientational preferences of the methylamine molecules at the liquid surface are clearly governed by the requirement of maximizing their hydrogen bonding interaction. As a consequence, methylamine molecules point by their apolar CH3 group straight to the vapour, while by the potential hydrogen bonding directions of the NH2 group flatly to the liquid phase. Further, within the surface layer, methylamine molecules stay, on average, noticeably farther from the bulk liquid phase than waters. Increasing methylamine mole fraction leads to the gradual breaking up of the lateral percolating H-bonding network of the surface molecules. Finally, methylamine molecules accelerate, while water molecules slow down the exchange of both species between the liquid surface and the bulk liquid phase. Further, methylamine molecules slow down the lateral diffusion of each other, and even prevent water molecules from showing noticeable lateral diffusion within the surface layer. The reason for this latter effect is that the mean residence time of the water molecules at the liquid surface becomes considerably shorter than the characteristic time of their lateral diffusion in the presence of methylamine.

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

Cited by 12 publications

References 63 publications

Adsorption of Formamide at the Surface of Amorphous and Crystalline Ices under Interstellar and Tropospheric Conditions. A Grand Canonical Monte Carlo Simulation Study

Adsorption of Formamide at the Surface of Amorphous and Crystalline Ices under Interstellar and Tropospheric Conditions. A Grand Canonical Monte Carlo Simulation Study

Adsorption of Methylamine on Amorphous Ice under Interstellar Conditions. A Grand Canonical Monte Carlo Simulation Study

Investigation of the liquid-vapour interface of aqueous methylamine solutions by computer simulation methods

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