We are interested in understanding the molecular force fields and potential energy surface. We use ab initio and DFT methods to study the structure, bonding and molecular vibrations. The force fields obtained by these methods on the optimized geometries of molecules are used to study the harmonic force fields in terms of force and compliance constants by performing normal mode analysis (NMA). A software is being developed locally for this purpose based on the QCPE program UMAT(#576). Several innovative ideas described in our publications for doing NMA are incorporated in this program to achieve the goal of automated vibrational analysis. The concept of orthogonal transformation, different scaling algorithms including scaled quantum mechanical (SQM) approach, determination of unique force constants for isotopomers of different symmetries, compliance constants in internal coordinates are some of the features available in the program. Since the real molecular potential is anharmonic, understanding the anharmonicity effects are important. For this purpose evaluations of symmetry unique cubic and quartic force constants, anharmonicity constants, Fermi resonance and vibration-rotation interaction constants of molecules are necessary. Work is in progress in this direction. Molecular symmetry is used to reduce the labour as much as possible. Infrared and Raman spectral intensities play a crucial role in understanding the electronic structure of molecules in terms of the derivatives of dipole moment and polarizability. This is another area of interest which is being explored The computed force and compliance constants are used to quantify the aromaticity, ionization constants and to explain the vibrational spectral features.

• Redundant internal coordinates, compliance constant and non-bonded interactions-some new insights, J. Chem. Sci., 125, 9 (2013).

• A relook at the compliance constants in redundant internal coordinates and some new insights, J. Chem. Phy., 131, 174112 (2009)

• Vibrational spectra of adamantanes X10H16 and diamantanes X14H20 (X=C,Si,Ge,Sn): A theoretical study, Theochem, 766, 125 (2006)

• Force field calculation of molecules in isotopomers of different symmetries in vibrational analysis, Theochem., 574, 245 (2001)

• Interpretation and accurate prediction of vibrational spectra- a modified ab initio scaled quantum mechanical approach, Theochem, 432, 139 (1998)

• Fulbright-Nehru Senior Research Fellow, 2010-2011.

• Visiting Professor, Department of Applied Chemistry, Tohoku University, Sendai, Japan, 2003.

• Indian Institute of Technology Kanpur, 1987-.

• Research Specialist, University of California, San Francisco, 1984-1987.

• Post-doctoral Research Associate, NIH Resource for NMR, Syracuse University, New York, 1983-1984.

Office

SL 206 ,
Department of Chemistry
IIT Kanpur,
Kanpur 208016

Office Phone: 0512-259-7340 (O)

Email: sm[AT]iitk.ac.in