  This paper presents a Graphics Processing Units (GPUs) implementation of the
Semiclassical Initial Value Representation (SC-IVR) propagator for vibrational
molecular spectroscopy calculations. The time-averaging formulation of the
SC-IVR for power spectrum calculations is employed. Details about the GPU
implementation of the semiclassical code are provided. Four molecules with an
increasing number of atoms are considered and the GPU-calculated vibrational
frequencies perfectly match the benchmark values. The computational time
scaling of two GPUs (NVIDIA Tesla C2075 and Kepler K20) respectively versus two
CPUs (Intel Core i5 and Intel Xeon E5-2687W) and the critical issues related to
the GPU implementation are discussed. The resulting reduction in computational
time and power consumption is significant and semiclassical GPU calculations
are shown to be environment friendly.
