Workshop on HPC in India Chemical Dynamics in Aqueous Media Amalendu Chandra Department of...

Workshop on HPC in India

Chemical Dynamics in Aqueous Media

Amalendu ChandraDepartment of Chemistry, Indian

Institute of Technology Kanpur, India 208016

ATIP 1st Workshop on HPC in India @ SC-09

A. Chandra ATIP 1st Workshop on HPC in India @ SC-09 2

Hydrogen bonded (tetrahedral) structure of water


Hydrogen bond fluctuations in water and aqueous solutions


Excess proton in water


Experimental Methods

X-ray and Neutron Scattering Low frequency Raman ( < 200 cm-1) Time Resolved Infrared Spectroscopy

Transient hole burning studies using IR laser


Pump-probe signal at different delay times

Variation of H-bond distance with time

Relaxation time ~ 1.0 psG.M.Gale etal PRL, 82, 1068 (1999)

= ~ 100-200 fs, ~ 1-2 ps A. Tokmakoff and coworkers JCP (2005) M.D. Fayer and coworkers, PNAS (2007)


Computation of Aqueous Systems


Ab initio Molecular Dynamics

Forces are calculated from electronic structure calculation that areperformed on-the-fly as the MD trajectory is generated.Car-Parrinello Method:

R. Car and M. Parrinello, Phys. Rev. Lett., 55, 2471 (1985) J. Hutter et al. CPMD, MPI Stuttgart and IBM Zurich


A. Chandra and coworkers, JPC/A (2008); JCP (2008)

OH stretch frequency vs time in OH stretch frequency vs time in liquid waterliquid water


Frequency vs hydrogen bond distance Frequency vs hydrogen bond distance (pure D(pure D22OO))


Dynamics of vibrational spectral diffusion:

Hole creation and subsequent dynamics from Hole creation and subsequent dynamics from nonequilibrium probability distributionsnonequilibrium probability distributions

Hole creation: Monte Carlo algorithm


Dynamics after hole creation: Excitation in Dynamics after hole creation: Excitation in blue/redblue/red

Experiments:G.M. Gale et al PRL (1999)


Time dependence of average frequency after Time dependence of average frequency after hole creationhole creation

1 ~ 100 fs (dynamics of intact hydrogen bonds) 2 ~ 2 ps (lifetimes of hydrogen bonds) s ~ 100 cm-1 (intermolecular stretching/bending vibrations)

A. Chandra and coworkers, JPC/A (2008); JCP (2009)


ScH2OSupercritical Supercritical waterwater

673K/0.0221

573K/0.0338423K/0.0334298K/0.0334

A.K Soper et al., JCP, 106, 249 (1996)A.K Soper et al., JCP, 106, 249 (1996)


Correlations between OD frequency and D..O distance

A. Chandra and coworkers,JPC/A (2008)


Proton Transfer in Proton Transfer in waterwaterEigen Eigen Zundel Zundel

complexcomplex


Mobility of H3O+ in liquid

water

D H3O+

= 9.31x10-5 cm2/s

DH2O = 2.30x10-5 cm2/s

Mobility of OH- in liquid water

D OH_ = 5.3x10-5 cm2/s

M.E. Tuckerman, D.Marx and M. Parrinello, Nature, 417, 925 (2002)A.Chandra, M. Tuckerman and D.Marx, PRL (2007); Acc. Chem. Res. (2006)

Proton Migration Dynamics


Protonic defects in water clusters

Where is the protonic defect located?Is there any proton transfer in clusters?

A. Bankura and A. Chandra, JCP (submitted)

Describes chemically relevant part of large system using quantum mechanics (QM) and rest by molecular mechanics (MM)

QM/MM Technique

Long Range (LR)

Short Range (SR)

QM Density

H3O+/OH- in different carbon nanotube systems

Effects of confinement

Quantum-classical simulations


Financial support:DST, CSIR, BRNS, MCIT (Government of India)AvH Foundation (Germany)

Group members:


IIT Kanpur ….

Workshop on HPC in India Chemical Dynamics in Aqueous Media Amalendu Chandra Department of...

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