STUDENT SEMINAR
Speaker: Ms. Sangita Mondal
Research Supervisor: Prof. Biman Bagchi
Topic: Thermodynamics and Kinetics of Nucleation: Application Towards Cloud Formation
Date & Time: Thursday, 27th October 2022 at 4:00 PM
Venue: SSCU Auditorium (Old Building)
Abstract:
Nucleation is a ubiquitous physical phenomenon observed in the kinetics of a large number of phase transformations which are characterized by first order phase transition. It has become particularly important in recent times because it provides the guiding principle in the synthesis of nanomaterials. According to thermodynamics, water should freeze at 0◦ C. However, one finds that, even below 0◦ C, pure water under homogeneous conditions can remain in liquid state for a long time as it continues to exist in a metastable state. The existence of such metastability is due to the presence of a barrier posed by first order phase transition and this necessitates nucleation. Nucleation is an activated process, where the formation of small nuclei of the stable new phase is hindered by a free energy barrier, and they can grow spontaneously to form the new phase only when the nuclei are larger than a certain critical size. To be more specific, nucleation provides the pathway of escape from metastability. The theory of nucleation phenomena was first proposed by Becker, Doring and Zelovich (BDZ). In this talk, first I shall discuss BDZ theory and its predictions and limitations. After that, I shall give a brief idea of heterogeneous nucleation and the Ostwald step rule.
Furthermore, the formation of ice in the Earth’s atmosphere changes the radiative properties of clouds and has a great impact on radiative balance and climate. It also plays a vital role in the global hydrological cycle. Aerosol particles (commonly referred to as ice nucleating particles [INPs]) play a crucial role in atmospheric ice formation processes. Here I shall discuss how organic aerosol particles contribute to INPs in the atmosphere. In addition, I will discuss different models which determine stable Ice Polymorph in Clouds.
References:
[1]Landau, L. D. and E. M. Lifshitz. 1969. Statistical Physics. Vol. 5. London: Pergamon Press.
[2]Bagchi, B. (2018). Statistical Mechanics for Chemistry and Materials Science. CRC Press.
[3]Wolf, M. J., Zhang, Y., Zawadowicz, M. A., Goodell, M., Froyd, K., Freney, E., … & Cziczo, D. J. (2020). A biogenic secondary organic aerosol source of cirrus ice nucleating particles. Nature communications, 11(1), 1-9.
[4]Hudait, A., &Molinero, V. (2016). What determines the ice polymorph in clouds?. Journal of the American Chemical Society, 138(28), 8958-8967