  A method for carrying out semiclassical initial value representation
calculations using first-principles molecular dynamics (FP-SC-IVR) is
presented. This method can extract the full vibrational power spectrum of
carbon dioxide from a single trajectory providing numerical results that agree
with experiment even for Fermi resonant states. The computational demands of
the method are comparable to those of classical single-trajectory calculations,
while describing uniquely quantum features such as the zero-point energy and
Fermi resonances. By propagating the nuclear degrees of freedom using
first-principles Born-Oppenheimer molecular dynamics, the stability of the
method presented is improved considerably when compared to dynamics carried out
using fitted potential energy surfaces and numerical derivatives.
