Academic department under which the project should be listed

CSM - Chemistry and Biochemistry

Faculty Sponsor Name

Martina Kaledin

Abstract (300 words maximum)

This project focuses on developing a novel computational technique to study molecular vibrations through infrared (IR) and Raman scattering Driven Molecular Dynamics (DMD) method. While the main criterion for IR absorption is a net change in the dipole moment in a molecule as it vibrates, presently we wish to predict and analyze vibrational spectra to study symmetric vibrational modes that are IR inactive or weakly active while strongly Raman active. A newly developed method was tested on CO2, H2O, CH4, and C20 molecules. Students optimized the molecular structures, obtained vibrational frequencies, and IR and Raman intensities. We used MP2/cc-pVDZ computational level to generate the potential energy surfaces (PES). Modified Hamilton’s equations of motion include a driven term with polarizability tensor surface (PTS), the function that couples the incoming and scattered lights. The resonant motions at fundamental frequencies were analyzed and described in terms of atomic displacements and absorbed energy profiles. All MP2 computations were carried out using Gaussian 16, MOLPRO program packages, and Fortran codes developed in our laboratory. This preliminary study shows promising results and provides key probes in the chemical identification of molecules. We show that it is possible to interpret experimental infrared and Raman spectra through a combination of ab initio molecular dynamics simulations and normal mode analysis. Future prospects of this method include exploration of the role of anharmonic effects.

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Molecular Vibrations of Symmetric Molecules: Raman Scattering Driven Molecular Dynamics Method

This project focuses on developing a novel computational technique to study molecular vibrations through infrared (IR) and Raman scattering Driven Molecular Dynamics (DMD) method. While the main criterion for IR absorption is a net change in the dipole moment in a molecule as it vibrates, presently we wish to predict and analyze vibrational spectra to study symmetric vibrational modes that are IR inactive or weakly active while strongly Raman active. A newly developed method was tested on CO2, H2O, CH4, and C20 molecules. Students optimized the molecular structures, obtained vibrational frequencies, and IR and Raman intensities. We used MP2/cc-pVDZ computational level to generate the potential energy surfaces (PES). Modified Hamilton’s equations of motion include a driven term with polarizability tensor surface (PTS), the function that couples the incoming and scattered lights. The resonant motions at fundamental frequencies were analyzed and described in terms of atomic displacements and absorbed energy profiles. All MP2 computations were carried out using Gaussian 16, MOLPRO program packages, and Fortran codes developed in our laboratory. This preliminary study shows promising results and provides key probes in the chemical identification of molecules. We show that it is possible to interpret experimental infrared and Raman spectra through a combination of ab initio molecular dynamics simulations and normal mode analysis. Future prospects of this method include exploration of the role of anharmonic effects.