Programme

P.19 -- Posters, VCTP-51

Date: Tuesday, 4 August 2026

Time: 09:30 - 10:30

ESTIMATING THE MAGNITUDE OF COHERENT RING CURRENT IN π-CONJUGATED AROMATIC MOLECULES

Ho Quang Huy (1,2)*, Quoc Thinh Banh (3), Phan Ngoc Loan (3), Hirobumi Mineo (4,5)

(1) Faculty of Engineering Technology, University of Phan Thiet, 225 Nguyen Thong, Phu Thuy, Lam Dong, Vietnam (2) Interdisciplinary Research Transfer and Innovation Center, University of Phan Thiet, 225 Nguyen Thong, Phu Thuy, Lam Dong, Vietnam (3) Computational Physics Laboratory K002, Department of Physics, Ho Chi Minh City University of Education, Ho Chi Minh City, Vietnam (4) Atomic Molecular and Optical Physics Research Group, Science and Technology Advanced Institute, Van Lang University, Ho Chi Minh City, Vietnam (5) Faculty of Applied Technology, School of Technology, Van Lang University, Ho Chi Minh City, Vietnam.

Photo-induced charge migration descibes the motion of an electron or a hole from one site to another within a molecule, and this process can be controlled by an external optical field. As a typical example of charge migration in π-conjugated aromatic molecules, coherent π-electron rotation can be generated by a laser pulse that excites a pair of degenerate excited states involved in the π-π* transition from the ground state. Within the traditional Hückel model, π molecular orbitals are represented as linear combinations of pz atomic orbitals. The ring current induced by such rotational electron motion can generate a magnetic field strong enough to be detected experimentally. Therefore, the magnitude of ring current is one of the key observable quantities in the development of molecular switching devices based on organic molecules. In a previous theoretical study [J. Chem. Phys. 138, 074304 (2013)], the current magnitude has been evaluated along the bonds connecting neighboring atoms in a molecular ring, a quantity known as the coherent bond current. Here, the coherent bond current was calculated in π-conjugated aromatic systems by combining an analytical approach with ab-initio calculations, in which the bond current formula was derived using the Slater type pz atomic orbitals. However, the Slater type pz orbitals are not fully consistent with the Gaussian basis sets commonly employed in modern ab initio calculations. This motivates us to formulate the coherent bond current using Gaussian type pz orbitals in π-conjugated systems, such as benzene, toluene and coronene. The proposed formulation provides a more consistent framework for evaluating coherent bond currents in conjunction with Gaussian-based electronic structure calculations.

Presenter: Ho Quang Huy