QM/MMpol: A consistent model for solute/solvent polarization. Application to the aqueous solvation and spectroscopy of formaldehyde, acetaldehyde, and acetone
- Pacific Northwest National Lab., Richland, WA (United States)
We present a hybrid quantum mechanical/molecular mechanical theory that consistently treats many-body polarization effects in the MM region (QM/MMpol). Here we extend the formalism to include analytical gradients, making the approach useful for molecular dynamics (MD) simulations. We present implementation details for NDDO semiempirical QM Hamiltonians of the MNDO type. We also present an analysis of the solvent and substituent effects on the spectroscopic blue shift of the n-{pi}{sup *} electronic excited state of a series of carbonyl-containing solutes: formaldehyde, acetaldehyde, and acetone. For formaldehyde, we present optimized structures, binding energies, and MD results for CH{sub 2}O/(H{sub 2}O){sub n} clusters (n = 1-6) and describe the effect of specific water/chromophore interactions. The MD results show that CH{sub 2}O/(H{sub 2}O){sub 3} exhibits the most favorable solvation with the solute and the three waters forming ringlike structures with near optimal hydrogen bonding interactions. The n = 3 cluster also has the largest solvent-induced blue shift of the clusters studied, with a value of 730 cm{sup -1} at 150 K. Aqueous bulk-phase MD simulations of formaldehyde, acetaldehyde, and acetone at 300 K show the average number of waters in the first solvation shell of the carbonyl oxygen is 1.2 (formaldehyde), 1.8 (acetaldehyde), and 2.2 (acetone). 60 refs., 16 figs., 3 tabs.
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 380778
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 34; Other Information: PBD: 22 Aug 1996
- Country of Publication:
- United States
- Language:
- English
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