qian-rui

Dr. Qian-Rui Huang

• E-mail: Append@gmail.com

Education

• • Sep. 2012 – Oct. 2016 Ph.D. in Chemistry, University College London (UCL)

  • Sep. 2008 – Aug. 2010 M.Sc. in Chemistry, National Taiwan University (NTU)

  • Sep. 2004 – Aug. 2008 B.Sc. in Chemistry, National Taiwan University (NTU)

Research  Interests

Vibrational Anharmonicity in Hydrogen-bonded systems

Vibrations are not harmonic. 

In many systems, especially the systems with hydrogen bonds or strong intermolecular interactions, the harmonic vibration analysis can lead to erroneous result that largely differ from experimental results; hence, anharmonicity is necessary in the vibrational analysis of these systems. 

One of the most significant phenomenon arise from vibrational anharmonicity is the Fermi-resonance between the stretching and bending overtones, which occurs in solvated hydronium systems.  

The vibrational motion of hydrogen bonded system are generally anharmonic due to the hydrogen bond, which reflects significant coupling between different normal modes. Hence, we're also interesting in alcohol clusters, amines, small organic molecules and their clusters.

In our group, we're using two method to deal with anharmonic vibrational analysis:

• • 1. Discrete-Variable Representation (DVR):

    2. We scan the potential energy surface (PES) and associate dipole moment function (DMF) on specific grid points which is generated for gaussian-hermite quadrature, then we can diagonalize the DVR Hamiltonian directly. We've utilized this approach to systems with 6 normal modes,[1] and we're now pushing the limit  to ~15 modes by carefully applying approximation schemes. Meanwhile, we're also developing tools to analyze the results from DVR calculations.

• 1. Ab-Initio Anharmonic Approach (AAA):

  2. We build the quatic potential with third and fourth derivates, which can be obtained from quantum chemistry packages, then the Hamiltonian can be expressed easily using vibrational ladder operator. We've utilized this approach to system with 25 normal modes,[2] and now we can apply this method to system with 25 modes within a few hours by properly parallized the generation of Hamiltonian matrix elements.

Reference

• • [1] Features in Vibrational Spectra Induced by Ar-tagging for H3O+Arm, m=0-3, J. Phys. Chem. A, 119, 10887–10892 (2015)

  • [2] An Ab-Initio anharmonic approach to study vibrational spectra of small ammonia clusters. Phys. Chem. Chem. Phys., 18, 30498–30506 (2016)