5 Introduction to Quantum Vibrational Spectroscopy
109
grid-based approaches should enable nearly exact prediction of NIR spectra of more
complex molecules, which will form an essential progress in our understanding of
NIR spectroscopy.
5.7 Summary and Future Prospects
Practical applications of the methods of quantum chemistry in NIR spectroscopy have
mostly been limited by their computational cost. In the recent decade, a remarkable rise in practical applications of theoretical calculations in NIR spectroscopy
was observed. This resulted from the development of quantum-based approaches
and their implementation, as well as from the progress in technology resulting in a
continuous increase in computational capacities. This allows for the anticipation of
further advances in the forthcoming years, and a twofold development can presently
be witnessed in this field. Firstly, studies of NIR spectra of increasingly complex
systems are becoming feasible. This opens new opportunities, as the complexity of
NIR spectra tends to scale steeply with the system size, and their interpretability
by conventional spectroscopic methods is limited. Secondly, highly accurate gridbased methods are capable of yielding nearly exact results. At the moment, computational complexity of grid-based methods limits their applicability to few-atom
systems. Nevertheless, they form an essential aid at the moment, as the established
‘universal’ anharmonic frameworks (e.g., VSCF, VPT2) have primarily been formulated with efficiency in mind. This could only be achieved through various approximations affecting their robustness and accuracy. Grid-based methods demonstrate
their usefulness in directly correcting VPT2 results for a few selected modes of
interest; this even applies for seemingly manageable modes such as OH stretching
vibrations. As the primary factors limiting the applicability of computational chemistry in NIR spectroscopy are consistently challenged, a general conclusion may be
drawn that in the next decade a markedly rapid expansion of NIR studies utilizing
methods of quantum chemistry will be observed.
References
1. D.C. Harris, M.D. Bertolucci, Symmetry and spectroscopy. An Introduction to Vibrational and
Electronic Spectroscopy (Dover Publications, INC., New York, 1980)
2. E.B. Wilson, J.C. Decius, P.C. Cross, Molecular Vibrations: The Theory of Infrared and Raman
Vibrational Spectra (Dover Publications, INC., New York, 1980)
3. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 6th
edn. (Wiley, Hoboken, New Jersey, 2009)
4. F.S. Levin, An Introduction to Quantum Theory (Cambridge University Press, 2002)
5. P. Pulay, G. Fogarasi, F. Pong, J.E. Boggs, Systematic ab initio gradient calculation of molecular
geometries, force constants, and dipole moment derivatives. J. Am. Chem. Soc. 101, 2550–2560
(1979)
109
grid-based approaches should enable nearly exact prediction of NIR spectra of more
complex molecules, which will form an essential progress in our understanding of
NIR spectroscopy.
5.7 Summary and Future Prospects
Practical applications of the methods of quantum chemistry in NIR spectroscopy have
mostly been limited by their computational cost. In the recent decade, a remarkable rise in practical applications of theoretical calculations in NIR spectroscopy
was observed. This resulted from the development of quantum-based approaches
and their implementation, as well as from the progress in technology resulting in a
continuous increase in computational capacities. This allows for the anticipation of
further advances in the forthcoming years, and a twofold development can presently
be witnessed in this field. Firstly, studies of NIR spectra of increasingly complex
systems are becoming feasible. This opens new opportunities, as the complexity of
NIR spectra tends to scale steeply with the system size, and their interpretability
by conventional spectroscopic methods is limited. Secondly, highly accurate gridbased methods are capable of yielding nearly exact results. At the moment, computational complexity of grid-based methods limits their applicability to few-atom
systems. Nevertheless, they form an essential aid at the moment, as the established
‘universal’ anharmonic frameworks (e.g., VSCF, VPT2) have primarily been formulated with efficiency in mind. This could only be achieved through various approximations affecting their robustness and accuracy. Grid-based methods demonstrate
their usefulness in directly correcting VPT2 results for a few selected modes of
interest; this even applies for seemingly manageable modes such as OH stretching
vibrations. As the primary factors limiting the applicability of computational chemistry in NIR spectroscopy are consistently challenged, a general conclusion may be
drawn that in the next decade a markedly rapid expansion of NIR studies utilizing
methods of quantum chemistry will be observed.
References
1. D.C. Harris, M.D. Bertolucci, Symmetry and spectroscopy. An Introduction to Vibrational and
Electronic Spectroscopy (Dover Publications, INC., New York, 1980)
2. E.B. Wilson, J.C. Decius, P.C. Cross, Molecular Vibrations: The Theory of Infrared and Raman
Vibrational Spectra (Dover Publications, INC., New York, 1980)
3. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 6th
edn. (Wiley, Hoboken, New Jersey, 2009)
4. F.S. Levin, An Introduction to Quantum Theory (Cambridge University Press, 2002)
5. P. Pulay, G. Fogarasi, F. Pong, J.E. Boggs, Systematic ab initio gradient calculation of molecular
geometries, force constants, and dipole moment derivatives. J. Am. Chem. Soc. 101, 2550–2560
(1979)