The most striking feature of femtosecond laser that has not been matched by any other material processing means is its ability to remove material with minimal collateral damage. The objective of this project is to perform Ab initio based multiscale modeling of thermal transport in femtosecond laser materials processing. The key challenge in the modeling is to establish a unified formulation that can correctly and effectively describe thermal transport in femtosecond laser materials processing without or with minimal empirical formulations. The Ab initio based multiscale approach can bridge the divide between the experiments and theories, and eliminate the needs of any assumption and empirical parameters. A quantum molecular dynamics (MD) simulation based on density function theory (DFT) will be carried out first to determine appropriate intermolecular potentials for classical MD simulation. A hybrid MD/semi-classical two-temperature multiscale model will be developed by combining classical MD simulation based on the intermolecular potentials obtained from quantum MD simulation together with the semi-classical energy equation for electrons. An inverse heat transfer modeling based on the semi-classical two-temperature model will be carried out to obtain the microscale transport properties, which are then used to develop the continuum model for materials removal. The stochastic modeling of femtosecond laser processing of metal under uncertainties of thermophysical and processing parameters will be carried out. Experiments on femtosecond laser processing of gold and copper by femtosecond laser pulses will be conducted in order to validate the Ab initial based multiscale and stochastic models developed under this project.
The Ab initio based multiscale and stochastic models will allow the users to select proper processing parameters to obtain the desired micro- and nanostructure; this will result in significant reduction of cost associated with the traditional trial-and-error approach and will increase the economic competitiveness of the United States on nanomanufacturing. The outcome of the research will be disseminated through publications in archival journals, presentations at national and international conferences, and student dissertations. The outreach activities will also help promoting the public awareness and recognition of science and engineering and promote the public image of scientists and engineers, which will play a very important role in education at all levels and will also have broader impacts on technology, economy, and society.
