scholarly journals Atmospheric Cluster Dynamics Code: a flexible method for solution of the birth-death equations

2011 ◽  
Vol 11 (9) ◽  
pp. 25263-25295 ◽  
Author(s):  
M. J. McGrath ◽  
T. Olenius ◽  
I. K. Ortega ◽  
V. Loukonen ◽  
P. Paasonen ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Rate Coefficients ◽  
Free Energies ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Initial Cluster ◽  
Sticking Probabilities ◽  
Quantum Chemical Data ◽  
Birth Death ◽  
Atmospherically Relevant

Abstract. The Atmospheric Cluster Dynamics Code (ACDC) is presented and explored. This program was created to study the first steps of atmospheric new particle formation by examining the formation of molecular clusters from atmospherically relevant molecules. The program models the cluster kinetics by explicit solution of the birth–death equations, using an efficient computer script for their generation and the MATLAB ode15s routine for their solution. Through the use of evaporation rate coefficients derived from formation free energies calculated by quantum chemical methods for clusters containing dimethylamine or ammonia and sulphuric acid, we have explored the effect of changing various parameters at atmospherically relevant monomer concentrations. We have included in our model clusters with 0–4 base molecules and 0–4 sulfuric acid molecules for which we have commensurable quantum chemical data. The tests demonstrate that large effects can be seen for even small changes in different parameters, due to the non-linearity of the system. In particular, the temperature and sticking probabilities both have a large impact on all clusters, while the boundary effects (allowing clusters to grow to sizes beyond the largest cluster that the code keeps track of, or forbidding such processes), coagulation sink terms, non-monomer collisions, and monomer concentrations can all have significant effects. Removal of coagulation sink terms prevented the system from reaching the steady state when all the initial cluster concentrations were set to the default value of 1 m−3, which is probably an effect caused by studying only relatively small cluster sizes.

scholarly journals Atmospheric Cluster Dynamics Code: a flexible method for solution of the birth-death equations

2012 ◽  
Vol 12 (5) ◽  
pp. 2345-2355 ◽  
Author(s):  
M. J. McGrath ◽  
T. Olenius ◽  
I. K. Ortega ◽  
V. Loukonen ◽  
P. Paasonen ◽  
...  
Keyword(s):  
Steady State ◽  
Quantum Chemical ◽  
Rate Coefficients ◽  
Free Energies ◽  
Quantum Chemical Methods ◽  
Initial Cluster ◽  
Sticking Probabilities ◽  
Quantum Chemical Data ◽  
Birth Death ◽  
Atmospherically Relevant

Abstract. The Atmospheric Cluster Dynamics Code (ACDC) is presented and explored. This program was created to study the first steps of atmospheric new particle formation by examining the formation of molecular clusters from atmospherically relevant molecules. The program models the cluster kinetics by explicit solution of the birth–death equations, using an efficient computer script for their generation and the MATLAB ode15s routine for their solution. Through the use of evaporation rate coefficients derived from formation free energies calculated by quantum chemical methods for clusters containing dimethylamine or ammonia and sulphuric acid, we have explored the effect of changing various parameters at atmospherically relevant monomer concentrations. We have included in our model clusters with 0–4 base molecules and 0–4 sulfuric acid molecules for which we have commensurable quantum chemical data. The tests demonstrate that large effects can be seen for even small changes in different parameters, due to the non-linearity of the system. In particular, changing the temperature had a significant impact on the steady-state concentrations of all clusters, while the boundary effects (allowing clusters to grow to sizes beyond the largest cluster that the code keeps track of, or forbidding such processes), coagulation sink terms, non-monomer collisions, sticking probabilities and monomer concentrations did not show as large effects under the conditions studied. Removal of coagulation sink terms prevented the system from reaching the steady state when all the initial cluster concentrations were set to the default value of 1 m−3, which is probably an effect caused by studying only relatively small cluster sizes.

scholarly journals Electrical charging changes the composition of sulfuric acid-ammonia/dimethylamine clusters

2014 ◽  
Vol 14 (2) ◽  
pp. 1317-1348 ◽  
Author(s):  
I. K. Ortega ◽  
T. Olenius ◽  
O. Kupiainen-Määttä ◽  
V. Loukonen ◽  
T. Kurtén ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Quantum Chemical ◽  
Measured Data ◽  
Free Energies ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Charged Clusters ◽  
Electrically Charged ◽  
Electrical Charging

Abstract. Sulfuric acid clusters stabilized by base molecules are likely to have a significant role in atmospheric new particle formation. Recent advances in mass spectrometry techniques have permitted the detection of electrically charged clusters. However, direct measurement of electrically neutral clusters is not possible. Mass spectrometry instruments can be combined with a charger, but the possible effect of charging on the composition of neutral clusters must be addressed before the measured data can be linked to properties of neutral clusters. In the present work we have used formation free energies from quantum chemical methods to calculate the evaporation rates of electrically charged (both positive and negative) sulfuric acid-ammonia/dimethylamine clusters. To understand how charging will affect the composition of these clusters, we have compared the evaporation rates of charged clusters with those of the corresponding neutral clusters. We found that the only cluster studied in this paper which will retain its composition is H2SO4 · NH3 when charged positively; all other clusters will be altered by both positive and negative charging. In the case of charging clusters negatively, base molecules will completely evaporate from clusters with 1 to 3 sulfuric acid molecules in the case of ammonia, and from clusters with 1 or 2 sulfuric acid molecules in the case of dimethylamine. Larger clusters will maintain some base molecules, but the H2SO4 : base ratio will increase. In the case of positive charging, some of the acid molecules will evaporate, decreasing the H2SO4 : base ratio.

scholarly journals From quantum chemical formation free energies to evaporation rates

2012 ◽  
Vol 12 (1) ◽  
pp. 225-235 ◽  
Author(s):  
I. K. Ortega ◽  
O. Kupiainen ◽  
T. Kurtén ◽  
T. Olenius ◽  
O. Wilkman ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Atmospheric Aerosols ◽  
Quantum Chemical ◽  
Local Minimum ◽  
Particle Formation ◽  
Free Energies ◽  
Chemical Methods ◽  
The Past ◽  
Quantum Chemical Methods ◽  
Stable Clusters

Abstract. Atmospheric new particle formation is an important source of atmospheric aerosols. Large efforts have been made during the past few years to identify which molecules are behind this phenomenon, but the actual birth mechanism of the particles is not yet well known. Quantum chemical calculations have proven to be a powerful tool to gain new insights into the very first steps of particle formation. In the present study we use formation free energies calculated by quantum chemical methods to estimate the evaporation rates of species from sulfuric acid clusters containing ammonia or dimethylamine. We have found that dimethylamine forms much more stable clusters with sulphuric acid than ammonia does. On the other hand, the existence of a very deep local minimum for clusters with two sulfuric acid molecules and two dimethylamine molecules hinders their growth to larger clusters. These results indicate that other compounds may be needed to make clusters grow to larger sizes (containing more than three sulfuric acid molecules).

scholarly journals From quantum chemical formation free energies to evaporation rates

2011 ◽  
Vol 11 (10) ◽  
pp. 27327-27357 ◽  
Author(s):  
I. K. Ortega ◽  
O. Kupiainen ◽  
T. Kurtén ◽  
T. Olenius ◽  
O. Wilkman ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Atmospheric Aerosols ◽  
Quantum Chemical ◽  
Local Minimum ◽  
Particle Formation ◽  
Free Energies ◽  
Chemical Methods ◽  
The Past ◽  
Quantum Chemical Methods ◽  
Stable Clusters

Abstract. Atmospheric new particle formation is an important source of atmospheric aerosols. Large efforts have been made during the past few years to identify which molecules are behind this phenomenon, but the actual birth mechanism of the particles is not yet well known. Quantum chemical calculations have proven to be a powerful tool to gain new insights into the very first steps of particle formation. In the present study we use formation free energies calculated by quantum chemical methods to estimate the evaporation rates of species from sulfuric acid clusters containing ammonia or dimethylamine. We have found that dimethylamine forms much more stable clusters with sulphuric acid than ammonia does. On the other hand, the existence of a very deep local minimum for clusters with two sulfuric acid molecules and two dimethylamine molecules hinders their growth to larger clusters. These results indicate that other compounds may be needed to make clusters grow to larger sizes (containing more than three sulfuric acid molecules).

Modelling Macroscopic Properties of Organic Species on the Basis of Quantum Chemical Analysis (on an Example of Inhibiting Efficiency of Ureides and Acetylides against Corrosion)

2014 ◽  
Vol 225 ◽  
pp. 7-12
Author(s):  
Georgy S. Beloglazov ◽  
Andrei A. Sikachina ◽  
Sergei M. Beloglazov
Keyword(s):  
Experimental Data ◽  
Dipole Moment ◽  
Quantum Chemical ◽  
Quantum Chemical Analysis ◽  
Chemical Methods ◽  
Organic Species ◽  
Quantum Chemical Methods ◽  
Homo And Lumo ◽  
Inhibitive Action ◽  
Quantum Chemical Data

The experimental data on efficiencies of a series of 7 ureides and 5 acetylides as inhibitors (IN) of corrosion of mild steel in Postgate B media compared to quantum chemical data; the following descriptors found to be essential to describe the inhibitive properties under given conditions: energies of the boundary molecular orbitals (HOMO and LUMO) and dipole moment. The inhibitive properties of the chosen ureides under given conditions are based on electron donating rather than accepting properties of their molecules. PM/3 method was found to be preferable compared to other quantum chemical methods used (i.e., MNDO, AM/1), and even non-empiricab initiomethods because it is found to be more helpful in explaining the mechanism of inhibitive action of organic species.

scholarly journals Energetics of LOHC: Structure-Property Relationships from Network of Thermochemical Experiments and in Silico Methods

Hydrogen ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 101-121
Author(s):  
Sergey P. Verevkin ◽  
Vladimir N. Emel’yanenko ◽  
Riko Siewert ◽  
Aleksey A. Pimerzin
Keyword(s):  
In Silico ◽  
Quantum Chemical ◽  
Structure Property ◽  
Chemical Methods ◽  
Key Technology ◽  
Structure Property Relationships ◽  
Quantum Chemical Methods ◽  
Dehydrogenation Reactions ◽  
Storage Technologies ◽  
In Silico Methods

The storage of hydrogen is the key technology for a sustainable future. We developed an in silico procedure, which is based on the combination of experimental and quantum-chemical methods. This method was used to evaluate energetic parameters for hydrogenation/dehydrogenation reactions of various pyrazine derivatives as a seminal liquid organic hydrogen carriers (LOHC), that are involved in the hydrogen storage technologies. With this in silico tool, the tempo of the reliable search for suitable LOHC candidates will accelerate dramatically, leading to the design and development of efficient materials for various niche applications.

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