Untersuchung der Dichte- und Temperaturabhängigkeit von Schwingungsrelaxationsprozessen in Wasser und Ammoniak mittels klassischer und semiklassischer molekulardynamischer Simulationen

• Applicant: Professor Dr. Jörg Schroeder
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2006 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 24430723

• Final Report Year: 2012

Final Report Abstract

One of the advantages of non-equilibrium simulations is that they provide complete information on the solvent response upon vibrational excitation and subsequent energy relaxation as a result of energy transfer to the intermolecular hydrogen bond. That allowed us to investigate the dependence of solvent structural dynamics on the state of the solute molecule, indicating different time scales for solvent restructuring in response to HOD molecule vibrational excitation and subsequent vibrational energy relaxation. The former stage leads to a slight increase in the average number of hydrogen bonds in the system. The important insight into the nature of pressure and temperature dependence of the number of hydrogen bonds in water can be achieved by combining the structural information obtained from molecular dynamics simulations with the measured absorbance frequency data. The established correlation between structural and spectroscopic quantities was used to make a connection to the average hydrogen bond connectivity in the fluid via the temperature and density dependent dielectric constant of water. Vibrational energy transfer from the excited ND-stretch of NH2D dissolved in liquid ammonia was studied by semiclassical molecular dynamics. The calculated relaxation rate was found to be in excellent agreement with experiment. Moreover, the analysis of the elucidated energy transfer channels allowed to explain the weak density dependence of the vibrational energy relaxation rate.

Publications

• Nonequilibrium molecular dynamics simulations of vibrational energy relaxation of HOD in D2O. J. Chem.Phys 2009, 130, 174507
  Kandratsenka, A.; Schroeder, J.; Schwarzer, D.; Vikhrenko, V. S.
  
• Vibrational energy relaxation of the ND-stretching vibration of NH2D in liquid NH3. Phys. Chem. Chem. Phys. 2012
  Schäfer, T.; Kandratsenka, A.; Vöhringer, P.; Schroeder, J.; Schwarzer, D.