On the importance of quantum mechanics for nanotechnology

In this article it is argued that classical molecular dynamics studies of nanomachines may not give an accurate representation of their performance. Fortunately a new method, internal coordinate quantum Monte Carlo, an improved technique for computing quantum mechanical ground-state energies and wavefunctions, has the potential capability to model these systems. Some relevant examples demonstrate that the quantum ground state for many-body systems similar to those of interest in nanotechnology has a qualitatively different structure than that obtained from a molecular dynamics calculation which exhibited chaos and gross instabilities at energies of only a fraction of the ground-state energy. This result casts uncertainty on the reliability of using the molecular dynamics method to calculate the structure or any other dynamical quantity relevant to nanotechnology.