### Multiscale Modeling and Computation of Optically Manipulated Nano Devices

- Series
- Applied and Computational Mathematics Seminar
- Time
- Monday, October 7, 2019 - 13:55 for 1 hour (actually 50 minutes)
- Location
- Skiles 005
- Speaker
- Professor Di Liu – Michigan State University

We present a multiscale modeling and computational scheme for optical-

mechanical responses of nanostructures. The multi-physical nature of

the problem is a result of the interaction between the electromagnetic

(EM) field, the molecular motion, and the electronic excitation. To

balance accuracy and complexity, we adopt the semi-classical approach

that the EM field is described classically by the Maxwell equations,

and the charged particles follow the Schr ̈oidnger equations quantum

mechanically. To overcome the numerical challenge of solving the high

dimensional multi-component many- body Schr ̈odinger equations, we

further simplify the model with the Ehrenfest molecular dynamics to

determine the motion of the nuclei, and use the Time- Dependent

Current Density Functional Theory (TD-CDFT) to calculate the

excitation of the electrons. This leads to a system of coupled

equations that computes the electromagnetic field, the nuclear

positions, and the electronic current and charge densities

simultaneously. In the regime of linear responses, the resonant

frequencies initiating the out-of-equilibrium optical-mechanical

responses can be formulated as an eigenvalue problem. A

self-consistent multiscale method is designed to deal with the well

separated space scales. The isomerization of Azobenzene is presented as a numerical example.