12.12. Fast and accurate methods for the estimation of thermodynamic properties of chemical compounds (Vuori)
Chemical thermodynamics is the study of energy changes associated with chemical reactions. Its theories allow, for example, to determine why some reactions take place while others do not, and how much energy is bound or released in the process. The practical application of chemical thermodynamics requires detailed information of the thermodynamic properties of molecules. Unfortunately, these properties are known in detail only for some thousands of compounds, whereas the number of different chemical species is calculated in millions.
Accurate modelling of thermodynamic properties requires powerful computers
In his research work, Hannu Vuori used quantum chemistry, a branch of science focused on the application of quantum physics to solve chemical problems with the help of computers. This allows the accurate prediction of molecular properties.
”The results obtained through calculations are in many cases much more accurate than the existing experimental data,” says Hannu Vuori.
”We could use the results to show inconsistencies in the experimental data as well as to identify both crude and systematic errors. This is understandable, because many experimental methods are highly error prone.” Quantum chemical methods employ systematically applied approximations that determine the accuracy of the overall method. The accuracy can be increased by reducing both the number and level of approximations, but the downside is that more time and computational resources are needed to perform the actual calculations.
”With the available resources, we could model molecules with up to a few tens of atoms. However, many compounds of industrial relevance are significantly bigger which means that accurate quantum chemical calculations would take months or even years,” says Vuori. ”For this reason, we have to use a different approach in order to get results in a reasonable timeframe.”
Estimation methods yield results much faster than quantum chemical calculations
Thermodynamic properties of molecules can also be estimated, because they depend systematically on the molecular structure and its various structural groups.
”Estimation methods are very fast, because they involve only simple calculations. The methods are also very accurate, provided that the compounds in question are similar and the thermochemical data available for them are sufficiently accurate,” Vuori explains. “In this work, the results from quantum chemical calculations were used to extend the group contribution method of Sidney Benson to compounds of phosphorus, silicon, and boron. This allows the estimation of thermodynamic properties of molecules involving these elements, be they big or small, with only a fraction of the cost of quantum chemical calculations.”
The results of the work can be used, for example, in industrial process design or to estimate the stability of chemical compounds. ”The biggest benefit that the results offer is the possibility to examine systems that have not yet been made to find out ones whose thermodynamic properties are best suited for different tasks. This is a huge opportunity,” Vuori concludes.
The thesis has been published in the JYU Dissertations series, number 581, Jyväskylä 2022. ISBN 978-951-39-9242-2 (PDF), URN:ISBN:978-951-39-9242-2, ISSN 2489-9003. Link to online version of the thesis:
Background information
Hannu Vuori completed his Matriculation Examination in 1967 and received his B.Sc. and M.Sc. degrees from the Ģֱ in 1971 and 1982, respectively. During his studies at the university, he worked as an elementary school teacher at various municipalities in Finland. After receiving his M.Sc. diploma, he joined Olivetti Suomi Oy as a software programmer and continued his career in IT Industry at Nokia Mobile Phones unit and later at Tieto Oyj. Since his retirement, he began doctoral studies at the Department of Chemistry, Ģֱ. The research has been funded by the Academy of Finland since 2019.
M.Sc. Hannu Vuori defends his doctoral dissertation ”Extending Benson Group Increment Theory to Compounds of Phosphorus, Silicon, and Boron with Computational Chemistry" at the Department of Chemistry, Ģֱ, lecture hall KEM4 on Monday 12th of December 2022 at 12:00. The opponent is Assistant Professor Antti Karttunen (Aalto University) and the Custos is Professor Heikki M. Tuononen (Ģֱ). The event is held in Finnish.
The audience can follow the dissertation in the lecture hall or online.
Link to the Zoom Webinar event (Zoom application or Google Chrome web browser recommended):