  In this work high-dimensional (21D) quantum dynamics calculations on
mode-specific surface scattering of a carbon monoxide molecule on a copper
(100) surface with lattice effects of a five-atom surface cell are performed
through the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH)
method. We employ a surface model in which five surface atoms near the impact
site are treated as fully flexible quantum particles while all other more
distant atoms are kept at fixed locations. To efficiently perform the 21D
ML-MCTDH wavepacket propagation, the potential energy surface is transferred to
canonical polyadic decomposition form with the aid of a Monte Carlo based
method. Excitation-specific sticking probabilities of CO on Cu(100) are
computed and lattice effects caused by the flexible surface atoms are
demonstrated by comparison with sticking probabilities computed for a rigid
surface. The dependence of the sticking probability of the initial state of the
system is studied, and it is found that the sticking probability is reduced,
when the surface atom on the impact site is initially vibrationally excited.
