Understanding Nonequilibrium Solute and Solvent Motions through Molecular Projections: Computer Simulations of Solvation Dynamics in Liquid Tetrahydrofuran (THF)

Journal of Physical Chemistry B

Volumn 107, Issue 51, 2003, Pages 14464-14475

  Bedard Hearn, Michael J ^a   Larsen, Ross E ^a   Schwartz, Benjamin J ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CHEMICAL RELAXATION; COMPUTER SIMULATION; DIFFUSION; GROUND STATE; MOLECULAR DYNAMICS; MONTE CARLO METHODS; NEGATIVE IONS; OXYGEN; ROTATION; SODIUM;

MOLECULAR PROJECTIONS; SOLVATION DYNAMICS;

ORGANIC SOLVENTS;

EID: 0345802848     PISSN: 15206106     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp035846e     Document Type: Article

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53. 15Our choice to use the solvation velocity response function, J(t), is based on high noise levels in the acceleration response function, B(t); the second derivative function B(t) varies too rapidly and our 400 nonequilibrium trajectories did not provide sufficient statistics to accurately integrate B(t) twice (as in eq 10b).
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63. These projections onto the first-shell and nearest neighbor molecules are not integrated. They were computed directly by selecting the appropriate subset of molecules in the nonequilibrium average for S(t), eq 1.
64. Figure 4a shows that the first solvent shell around the anion is both farther away (7.5 Å) than the neutral (6.5 Å) and contains more solvent molecules (12-13) than the neutral (8-9). We performed the nonequilibrium solute first-shell projections both for molecules within 6.5 and for molecules within 7.5 Å; this change of the first-shell definition only changed its contribution by ∼1 or 2%.
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68. However, solvation for this system occurs in the opposite manner to Onsager's famous "inverse snowball" (ref 51). See, for example: (a) ref 45. (b) Papazyan, A.; Maroncelli, M. J. Chem. Phys. 1993, 98 (8), 6431. (c) Fonseca, T.; Ladanyi, B. M. J. Phys. Chem. 1991, 95, (6) 2116.
69. Even though we will examine only the unoccupied anion state to describe the nonequilibrium solvation dynamics, the dynamics are driven only by the neutral solvent-solvent interactions. That is, modulation of the anion energy by solute or solvent motions is motivated not by the anion but by the new interactions with the now-occupied neutral state.
70. anion (not shown).
71. The translational projections onto the anion solvation energy (not shown) are nearly identical to the translational projections of the total solvation energy gap shown in Figure 6a.
72. anion dash-dot curve, Figure 8) results solely from first-shell solvent rotations because the LJ potential is so short-ranged.
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