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Simulation of water carbon nanotube system including chloroform Lin Chen Advisor: David Smith October 4, 2006
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H2OH2O H 2 O and CHCl 3 Two System Chloroform water CNT system Water CNT system
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Overview of Talk Why we study this topic System set up initial the system movement trial insert and delete trial energy calculation Water CNT system Chloroform CNT system Further research
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Target Adsorption of pollutants toxins biothreat agents Novel water purification materials development Why the CNT show more powerfull adsorption than activated carbon?
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initial the system + Length: 31.748 Angstrom Diameter: 8.1 Angstrom Type: Armchair 6,6 31.748 Angstrom H2O T 298.15K
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Lennard-Jones Potential Water σ 3.166 Angstrom ε 0.650 KJ mol-1 q H +0.4238 q O -0.8476 r OH 1 Angstrom r HH 1.63 Angstrom
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Chloroform σ CH 3.8 Angstrom ε CH 0.3344 KJ mol-1 σ Cl 3.47Angstrom ε Cl 1.672 KJ mol-1 σ C 3.4 Angstrom ε C 0.2325 KJ mol-1 Carbon r_CH_Cl 1.758 Angstrom angle_Cl_CH_Cl 111.3 q CH +0.42 q Cl -0.14 ‘united atom’ CH
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movement trial acc(o->n) = exp[-(U(n)-U(o))/k b T] accept U(n) < U(o) rand n) move the particle from old position to new position and orientation Accept factor Monte Carlo method
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Optimization of Movemenmt Parameters Translational move single-particle trial move Orientational move quaternion mscale1=0.07 mscale=0.7 mscale mscale1 mscale(CHCl 3 ) mscale1(CHCl 3 ) pure water 0.7 0.03 CHCl 3 solution 0.5 0.05 1.1 0.07 Final choice
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insert and delete trial insert delete Insert 'trial particle' at random place/orientation Calculate u s (single particle energy) accept or reject based on accept factor Acceptfactor = R * (exp(u s -u o )/k b T Randomly select 'trial particle' Calculate u s (single particle energy) accept or reject the trial based on accept factor Acceptfactor = R ’ * (exp(u o -u s )/k b T u 0 chose to represent pure H 2 O at room temperature and normal pressure.
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Fluctuation of water number the system arrive equilibrium
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energy calculation boundary condition image Energy = L-J + Coulomb Coulomb take long distance coulomb (ewald)
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Water CNT system Radial distribution
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Chloroform water CNT system Number of CHCl 3 50 Radial distribution
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w(r)=-K b Tln(g(r)) which represent ‘free energy’
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Number of CHCl 3 20 CH Radial Distribution O Radial Distribution
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Further Research Reduce the number of CHCl 3 in the system Conjunction of CNT
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Reference Frenkel, D.; Smit, B. Molecular Simulation from Algorithms to Applications: Elsevier, 1996. Hummer, G.; Rasalah, J. C. & Noworyta, J. P. Nature. 2001, 414, 188-190. Striolo, A.; Chialvo, A. A.; Gubbins, K. E. & Cummings, P. T. J. Chem. Phys. 2005,122, 234712. Mezei, M. Molecular Simulation, 1992, 9, 257-261. Mcdonald, N. A.; Carlson, H. A. & Jorgensen, W. L. J. Phys. Org. Chem. 1997, 10, 563-567.
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