About the Speaker

My primary field of expertise lies in molecular simulations of plasma-material interactions, particularly in the context of nuclear fusion. While my application of plasma technology to plant growth is relatively recent, I aim to discuss the importance of quantum dynamical processes of electrons to understand the interactions between plasma-generated reactive species and surfaces. To illustrate this, I will focus on specific examples involving plant seed surfaces. 

Abstract

Reactive Pathways of Plasma-Generated Molecules and Plant Seed Surfaces Using Density Functional Theory

Enhanced germination and DNA methylation have been observed when plasma is applied to plant seeds. If we can control the properties of seeds with plasma, we may be able to commit to a stable food supply. To do this, we need to understand the mechanisms by which plasma affects plant seeds. In particular, we are interested in how plasma or its effects pass through the seed coat and reach the inside of the seed.

In fusion science, we have investigated plasma-wall interaction using multi-scale molecular simulations. We apply this methodology to study the plasma-seed coat interaction. The calculations are performed using density functional theory (DFT). A popular analysis of chemical reactions using DFT is the estimation of activation barrier energies. In addition, we try to calculate the free energy barrier for real environments with finite temperatures.

The most interesting question is whether all reactive molecules generated in plasma are always neutral in the electronic state. If reactive molecules are in an ionic state, they are expected to react with seed coat molecules quite differently from the neutral state. Such phenomena cannot be treated by DFT and are instead treated by time-dependent density functional theory (TDDFT) calculations. Using our recently developed code QUMASUN [1], we demonstrate the difference in reaction processes between neutral and ionized cases.

[1] A. M. Ito, Y. Toda, A. Takayama, Nucl. Mater. & Energy, 42, 101836 (2025).