A concurrent multiscale finite difference time domain/molecular dynamics method for bridging an elastic continuum to an atomic system

A multiscale methodology that couples a finite difference time domain (FDTD) system (representing an elastic continuum) and an atomistic molecular dynamics (MD) system is proposed. The handshaking involves a parallel coupling of both the length and timescale. The FDTD-MD 'interface' is probed by a wave packet and the elastic impedance mismatch between the two systems is studied by examining the part of the probing wave packet that gets reflected from the interface. The reflected part is characterized in both temporal and frequency domains. Results show that only a small part of the wave is reflected from the interface, indicating a near seamless bridging of the two systems. Further, thermalization of the MD region results in transmission of additional energy into the FDTD region, with the transmitted energy corresponding to frequencies much higher than the central frequency of the probing wave packet. A characteristic resonant frequency exists between the MD and the FDTD regions, which is a result of a feedback between the two regions.