The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Hanna Vehkamäki - One of the best experts on this subject based on the ideXlab platform.
-
Quantum chemical studies on peroxodisulfuric Acid-sulfuric Acid-Water clusters
Computational and Theoretical Chemistry, 2011Co-Authors: Martta Toivola, Theo Kurtén, Ismael K. Ortega, Markku R. Sundberg, Ville Loukonen, Agílio A. H. Pádua, Hanna VehkamäkiAbstract:We have applied a multistep quantum chemistry method to study the formation energetics and binding patterns of sulfuric Acid–peroxodisulfuric Acid–Water clusters, with special focus on the O–O bridge. The length of the O–O bridge correlates linearly with the average length of S–O bonds next to it. The clustering of peroxodisulfuric Acid with sulfuric Acid and Water is thermodynamically favorable, as is the replacement by peroxodisulfuric Acid of one (but only one) of the sulfuric Acid molecules in a sulfuric Acid–Water cluster. However, the presence of H2S2O8 does not enhance the addition of sulfuric Acid to the clusters.
-
amines are likely to enhance neutral and ion induced sulfuric Acid Water nucleation in the atmosphere more effectively than ammonia
Atmospheric Chemistry and Physics, 2008Co-Authors: Theo Kurtén, Hanna Vehkamäki, Ville Loukonen, Markku KulmalaAbstract:We have studied the structure and formation thermodynamics of dimer clusters containing H 2 SO 4 or HSO 4 − together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine-H 2 SO 4 complexes is significantly stronger than that of NH 3 •H 2 SO 4 , while most amine-HSO 4 − complexes are only somewhat more strongly bound than NH 3 •HSO 4 − . Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H 2 SO 4 molecules or one H 2 SO 4 molecule and one HSO 4 − ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H 2 SO 4 co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric Acid-Water nucleation in the atmosphere.
-
Structure of Sulfuric Acid–Water Clusters
Nucleation and Atmospheric Aerosols, 2007Co-Authors: Martta Salonen, Ismo Napari, Hanna VehkamäkiAbstract:We have studied sulfuric Acid-Water clusters using molecular dynamics method. We have first simulated clusters containing Water and undissociated sulfuric Acid molecules. To explore the influence of molecular dissociation on cluster struc- ture, we have also studied clusters containing Water and bisulfate-hydronium ion pairs. Simulations show that sulfuric Acid tends to lie on the cluster surface whereas bisulfate is inside.
-
an improved parameterization for sulfuric Acid Water nucleation rates for tropospheric and stratospheric conditions
Journal of Geophysical Research, 2002Co-Authors: Hanna Vehkamäki, Ismo Napari, Madis Noppel, Markku Kulmala, K E J Lehtinen, Claudia Timmreck, A LaaksonenAbstract:[1] In this paper we present parameterized equations for calculation of sulfuric Acid–Water critical nucleus compositions, critical cluster radii and homogeneous nucleation rates for tropospheric and stratospheric conditions. The parameterizations are based on a classical nucleation model. We used an improved model for the hydrate formation relying on ab initio calculations of small sulfuric Acid clusters and on experimental data for vapor pressures and equilibrium constants for hydrate formation. The most rigorous nucleation kinetics and the thermodynamically consistent version of the classical binary homogeneous nucleation theory were used. The parameterized nucleation rates are compared with experimental ones, and at room temperature and relative humidities above 30% they are within experimental error. At lower temperatures and lower humidities the agreement is somewhat poorer. Overall, the values of nucleation rates are increased compared to a previous parameterization and are within an order of magnitude compared with theoretical values for all conditions studied. The parameterized equations will reduce the computing time by a factor 1/500 compared to nonparameterized nucleation rate calculations and therefore are in particular useful for large-scale models. The parameterized formulas are valid at temperatures between 230.15 K and 305.15 K, relative humidities between 0.01% and 100%, and sulfuric Acid concentrations from 104 to 1011 cm−3. They can be used to extrapolate the classical results down to 190 K. The parametrization is limited to cases where nucleation rates are between 10−7 and 1010 cm−3s−1, and the critical cluster contains at least four molecules.
-
An improved model for hydrate formation in sulfuric Acid–Water nucleation
Journal of Chemical Physics, 2002Co-Authors: Madis Noppel, Hanna Vehkamäki, Markku KulmalaAbstract:The formation of sulfuric Acid–Water hydrates in the vapor phase and nucleation rates of sulfuric Acid–Water clusters are investigated. The result of ab initio calculations and experimental data related to hydrates are utilized to improve the description of sulfuric Acid–Water hydration and nucleation in atmospheric conditions. The nucleation rates are obtained using the most rigorous nucleation kinetics and the thermodynamically consistent version of the classical nucleation model. The improvements increase the predicted nucleation rates compared to previous models. The predicted nucleation rates are compared with experimental ones, and they are in most cases within experimental errors. Some experimental evidence suggests that the present model gives a more realistic dependence of nucleation rate on relative humidity and sulfuric Acid concentration than the earlier versions of the theory.
R D Sanderson - One of the best experts on this subject based on the ideXlab platform.
-
self assembly and influence of the organic counterion in the ternary systems dodecylamine acrylic Acid Water and dodecylamine methacrylic Acid Water
Journal of Colloid and Interface Science, 2005Co-Authors: Patrice C Hartmann, Philippe Dieudonne, R D SandersonAbstract:Due to complete proton transfer from the Acid to the amine, a reaction between an equimolar mixture of dodecylamine and (meth)acrylic Acid leads to the formation of dodecylammonium (meth)acrylate. The latter can be considered as a surfactant with a polymerizable organic counterion. The ternary phase diagrams of the two systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water are described. Both systems can form isotropic solutions and lyotropic liquid crystalline lamellar phases. Moreover, the system with the methacrylate counterion can also form a cubic phase in the Water-rich part of the phase diagram. The difference in the self-organization observed for the two systems is explained by the greater bulkiness and hydrophobicity of the methacrylate. Whereas the acrylate counterion behaves rather like a classic inorganic counterion, the methacrylate counterion resides in the outermost part of the aggregates, giving rise to a change in the surface curvature.
-
Self-assembly and influence of the organic counterion in the ternary systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water
Journal of Colloid and Interface Science, 2005Co-Authors: Patrice C Hartmann, Philippe Dieudonne, R D SandersonAbstract:Due to complete proton transfer from the Acid to the amine, a reaction between an equimolar mixture of dodecylamine and (meth)acrylic Acid leads to the formation of dodecylammonium (meth)acrylate. The latter can be considered as a surfactant with a polymerizable organic counterion. The ternary phase diagrams of the two systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water are described. Both systems can form isotropic solutions and lyotropic liquid crystalline lamellar phases. Moreover, the system with the methacrylate counterion can also form a cubic phase in the Water-rich part of the phase diagram. The difference in the self-organization observed for the two systems is explained by the greater bulkiness and hydrophobicity of the methacrylate. Whereas the acrylate counterion behaves rather like a classic inorganic counterion, the methacrylate counterion resides in the outermost part of the aggregates, giving rise to a change in the surface curvature.
Markku Kulmala - One of the best experts on this subject based on the ideXlab platform.
-
amines are likely to enhance neutral and ion induced sulfuric Acid Water nucleation in the atmosphere more effectively than ammonia
Atmospheric Chemistry and Physics, 2008Co-Authors: Theo Kurtén, Hanna Vehkamäki, Ville Loukonen, Markku KulmalaAbstract:We have studied the structure and formation thermodynamics of dimer clusters containing H 2 SO 4 or HSO 4 − together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine-H 2 SO 4 complexes is significantly stronger than that of NH 3 •H 2 SO 4 , while most amine-HSO 4 − complexes are only somewhat more strongly bound than NH 3 •HSO 4 − . Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H 2 SO 4 molecules or one H 2 SO 4 molecule and one HSO 4 − ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H 2 SO 4 co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric Acid-Water nucleation in the atmosphere.
-
an improved parameterization for sulfuric Acid Water nucleation rates for tropospheric and stratospheric conditions
Journal of Geophysical Research, 2002Co-Authors: Hanna Vehkamäki, Ismo Napari, Madis Noppel, Markku Kulmala, K E J Lehtinen, Claudia Timmreck, A LaaksonenAbstract:[1] In this paper we present parameterized equations for calculation of sulfuric Acid–Water critical nucleus compositions, critical cluster radii and homogeneous nucleation rates for tropospheric and stratospheric conditions. The parameterizations are based on a classical nucleation model. We used an improved model for the hydrate formation relying on ab initio calculations of small sulfuric Acid clusters and on experimental data for vapor pressures and equilibrium constants for hydrate formation. The most rigorous nucleation kinetics and the thermodynamically consistent version of the classical binary homogeneous nucleation theory were used. The parameterized nucleation rates are compared with experimental ones, and at room temperature and relative humidities above 30% they are within experimental error. At lower temperatures and lower humidities the agreement is somewhat poorer. Overall, the values of nucleation rates are increased compared to a previous parameterization and are within an order of magnitude compared with theoretical values for all conditions studied. The parameterized equations will reduce the computing time by a factor 1/500 compared to nonparameterized nucleation rate calculations and therefore are in particular useful for large-scale models. The parameterized formulas are valid at temperatures between 230.15 K and 305.15 K, relative humidities between 0.01% and 100%, and sulfuric Acid concentrations from 104 to 1011 cm−3. They can be used to extrapolate the classical results down to 190 K. The parametrization is limited to cases where nucleation rates are between 10−7 and 1010 cm−3s−1, and the critical cluster contains at least four molecules.
-
An improved model for hydrate formation in sulfuric Acid–Water nucleation
Journal of Chemical Physics, 2002Co-Authors: Madis Noppel, Hanna Vehkamäki, Markku KulmalaAbstract:The formation of sulfuric Acid–Water hydrates in the vapor phase and nucleation rates of sulfuric Acid–Water clusters are investigated. The result of ab initio calculations and experimental data related to hydrates are utilized to improve the description of sulfuric Acid–Water hydration and nucleation in atmospheric conditions. The nucleation rates are obtained using the most rigorous nucleation kinetics and the thermodynamically consistent version of the classical nucleation model. The improvements increase the predicted nucleation rates compared to previous models. The predicted nucleation rates are compared with experimental ones, and they are in most cases within experimental errors. Some experimental evidence suggests that the present model gives a more realistic dependence of nucleation rate on relative humidity and sulfuric Acid concentration than the earlier versions of the theory.
-
Parameterizations for sulfuric Acid/Water nucleation rates
Journal of Geophysical Research, 1998Co-Authors: Markku Kulmala, Ari Laaksonen, Liisa PirjolaAbstract:We present parameterized equations for calculation of sulfuric Acid/Water critical nucleus compositions and homogeneous nucleation rates. The parameterizations are in agreement with the thermodynamically consistent version of classical binary homogeneous nucleation theory [Wilemski, 1984] incorporating the hydration effect. The new parameterizations produce nucleation rates that differ by several orders of magnitude from the rates predicted by other parameterizations available in the literature. Model simulations of atmospheric aerosol formation show that the use of the new parameterizations may in some cases result in simulated nucleation mode particle number densities that are by a factor of 1000 lower than those obtained using the old parameterizations.
Patrice C Hartmann - One of the best experts on this subject based on the ideXlab platform.
-
self assembly and influence of the organic counterion in the ternary systems dodecylamine acrylic Acid Water and dodecylamine methacrylic Acid Water
Journal of Colloid and Interface Science, 2005Co-Authors: Patrice C Hartmann, Philippe Dieudonne, R D SandersonAbstract:Due to complete proton transfer from the Acid to the amine, a reaction between an equimolar mixture of dodecylamine and (meth)acrylic Acid leads to the formation of dodecylammonium (meth)acrylate. The latter can be considered as a surfactant with a polymerizable organic counterion. The ternary phase diagrams of the two systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water are described. Both systems can form isotropic solutions and lyotropic liquid crystalline lamellar phases. Moreover, the system with the methacrylate counterion can also form a cubic phase in the Water-rich part of the phase diagram. The difference in the self-organization observed for the two systems is explained by the greater bulkiness and hydrophobicity of the methacrylate. Whereas the acrylate counterion behaves rather like a classic inorganic counterion, the methacrylate counterion resides in the outermost part of the aggregates, giving rise to a change in the surface curvature.
-
Self-assembly and influence of the organic counterion in the ternary systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water
Journal of Colloid and Interface Science, 2005Co-Authors: Patrice C Hartmann, Philippe Dieudonne, R D SandersonAbstract:Due to complete proton transfer from the Acid to the amine, a reaction between an equimolar mixture of dodecylamine and (meth)acrylic Acid leads to the formation of dodecylammonium (meth)acrylate. The latter can be considered as a surfactant with a polymerizable organic counterion. The ternary phase diagrams of the two systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water are described. Both systems can form isotropic solutions and lyotropic liquid crystalline lamellar phases. Moreover, the system with the methacrylate counterion can also form a cubic phase in the Water-rich part of the phase diagram. The difference in the self-organization observed for the two systems is explained by the greater bulkiness and hydrophobicity of the methacrylate. Whereas the acrylate counterion behaves rather like a classic inorganic counterion, the methacrylate counterion resides in the outermost part of the aggregates, giving rise to a change in the surface curvature.
Philippe Dieudonne - One of the best experts on this subject based on the ideXlab platform.
-
self assembly and influence of the organic counterion in the ternary systems dodecylamine acrylic Acid Water and dodecylamine methacrylic Acid Water
Journal of Colloid and Interface Science, 2005Co-Authors: Patrice C Hartmann, Philippe Dieudonne, R D SandersonAbstract:Due to complete proton transfer from the Acid to the amine, a reaction between an equimolar mixture of dodecylamine and (meth)acrylic Acid leads to the formation of dodecylammonium (meth)acrylate. The latter can be considered as a surfactant with a polymerizable organic counterion. The ternary phase diagrams of the two systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water are described. Both systems can form isotropic solutions and lyotropic liquid crystalline lamellar phases. Moreover, the system with the methacrylate counterion can also form a cubic phase in the Water-rich part of the phase diagram. The difference in the self-organization observed for the two systems is explained by the greater bulkiness and hydrophobicity of the methacrylate. Whereas the acrylate counterion behaves rather like a classic inorganic counterion, the methacrylate counterion resides in the outermost part of the aggregates, giving rise to a change in the surface curvature.
-
Self-assembly and influence of the organic counterion in the ternary systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water
Journal of Colloid and Interface Science, 2005Co-Authors: Patrice C Hartmann, Philippe Dieudonne, R D SandersonAbstract:Due to complete proton transfer from the Acid to the amine, a reaction between an equimolar mixture of dodecylamine and (meth)acrylic Acid leads to the formation of dodecylammonium (meth)acrylate. The latter can be considered as a surfactant with a polymerizable organic counterion. The ternary phase diagrams of the two systems dodecylamine/acrylic Acid/Water and dodecylamine/methacrylic Acid/Water are described. Both systems can form isotropic solutions and lyotropic liquid crystalline lamellar phases. Moreover, the system with the methacrylate counterion can also form a cubic phase in the Water-rich part of the phase diagram. The difference in the self-organization observed for the two systems is explained by the greater bulkiness and hydrophobicity of the methacrylate. Whereas the acrylate counterion behaves rather like a classic inorganic counterion, the methacrylate counterion resides in the outermost part of the aggregates, giving rise to a change in the surface curvature.