Classical nuclear motion: Does it fail to explain reactions and spectra in certain cases?

Is a classical description of nuclear motion sufficient when describing chemical reactions and spectra? This question is interesting because many researchers use in molecular dynamics simulations. The present paper investigates some phenomena that were previously attributed to quantum effects. if these can be modeled with traditional Car–Parrinello dynamics, is, method which treats classically widely applied the simulation spectra. We find for investigated system no additional paradigm needed reactions. special reactivity observed carbenes environment represented by noble gas matrix an transition state was not considered before. Also infrared spectrum porphycene perfectly dynamics. More studies are necessary decide what extent replace mechanical description.