From moelcular dynamics to kinetic rate theory: a simple example of multiscale modeling

摘要

Radiation damage formation in iron has been investigated using he method of molecular dynamics simulation. The MD simulations have been used to determine primary defect production parameters for cascade energies up to 50 keV at temperatures from 100 to 900K. The energy dependence of these parameters has been used to determine appropriate neutron-energy-spectrum averaged damage production cross sections for various iradiation enviroonments. Two applications of these effective cross sections are discussed. The first is an evaluation of neutron energy spectrum effects in commercial fission reactor pressure vessels. TRhe second example deals with the use of these cross sections in the source term of a kinetic model used to predict void selling and microstructural evolution. The simulation of the primary damage event by MD involves times less than 100 ps and a size scale of a few tens of nm, while the kinetic simulation encompass es several years and macroscopic sizes. This use of the MD results to develop and improved source term for rate theory modeling provides a simple example of multiscale modeling.