Linear discrete breather in fcc metals

Abstract

Nonlinear vibrational mode localized in two spatial dimensions and delocalized in the third dimension is studied for the first time in defect-free single crystals of fcc metals (Al, Cu and Ni) using molecular-dynamics methods. Interactions between atoms are described via standard embedded atom method potentials. All calculations are performed at zero temperature, which enables the observation of the studied phenomenon in the most transparent form. The vibrational mode is excited in a close-packed atomic chain along the [101¯] crystallographic direction in the three-dimensional computational cell by initial displacement of odd and even atoms in opposite directions along the chain. The maximal lifetime of the studied vibrational mode is found to be in the range of 15–17 ps, which corresponds to 140–160 oscillations. This mode in the fcc metals has a hard type nonlinearity, i.e. its frequency increases with increasing amplitude. The mode can accumulate vibrational energy in the range of 0.9–3.0 eV per atom. The initially excited atoms have the largest vibration amplitudes, while the amplitudes of other atoms decrease exponentially with deviation from the excited atomic chain. Such vibrational mode extended along single atomic chain is called here linear discrete breather in contrast to the studied so far zero-dimensional discrete breathers localized in all three spatial dimensions. This work reports a new type of discrete breather in three-dimensional lattices of fcc metals.