544 research outputs found
Theoretical study of the SN2 reaction of Cl-(H2O)+CH3Cl using the ONIOM-PCM method
No full textThe effects of solvation in the SN2 reaction Cl-(H2O)+CH3Cl were investigated using our own Nlayered integrated molecular orbital and molecular mechanics (ONIOM) polarizable continuum model (PCM) method [Vreven T, Mennucci B, da Silva CO, Morokuma K, Tomasi J (2001) J Chem Phys 115:62–72], which surrounds the microsolvated ONIOM system with a polarizable continuum. The micro solvating water molecule tends to stay in the vicinity of the original chloride ion. In the ONIOM calculations, Cl-+CH3Cl was considered as the ‘‘model’’ system and was handled with the ‘‘high-level’’ method, while the explicit water molecule in the microsolvated complex was treated at the ‘‘low-level’’. The molecular orbital (MO) and ONIOM(MO:MO) calculations allow us to assess the errors introduced by the ONIOM extrapolation, as well as the effects of microsolvation on the potential-energy surfaces. We find that ONIOM[B3LYP/6-31+G(d,p):HF/6-31+G(d,p)] and ONIOM[B3LYP/6-31+G(d,p):HF/6-31+G(d,p)]-PCM methods are good approximations to the target B3LYP/6-31+G(d,p) and B3LYP/6-31+G(d,p)-PCM methods. In addition, severalapproximate (computationally less expensive) schemes in the ONIOM-PCM method have been compared to the exact scheme, and all are shown to perform well
Theoretical study of the potential stability of the peroxo nitrate radical
No full textEisfeld W, Morokuma K. Theoretical study of the potential stability of the peroxo nitrate radical. JOURNAL OF CHEMICAL PHYSICS. 2003;119(9):4682-4688
MOLECULAR INTERACTIONS IN EXCITED STATES
No full textAuthor Institution: Department of Chemistry, The University of RochesterInteractions of an excited state molecule with ground state molecules have important implications in emission and photochemical processes in solutions. In this report the electron hole potential (EHP)SCF method we proposed is applied to ab initio calculations of and states of and acrolein interacting with Furthermore, the EHP method is extended to multi-configurational wave functions. This allows one to study the interaction between a ground state molecule and an excited state molecule of the same kind, such as excited dimers. The method is applied to lower excited states of formic acid dimer mainly to examine the potential energy curve for the symmetric proton transfer and the splitting of the monomers’ electronic transitions due to the interaction. K. Morokuma and S. Iwata, Chemical Physics Letters 16, 192 (1972)
Investigation of the vertical and adiabatic excitation spectrum of NO3
No full textEisfeld W, Morokuma K. Investigation of the vertical and adiabatic excitation spectrum of NO3 . The Journal of Chemical Physics. 2001;114(21):9430-9440
Theoretical study of the photoelectron spectrum of NO3 and the excited states of NO3+. I. Electronic spectrum
No full textEisfeld W, Morokuma K. Theoretical study of the photoelectron spectrum of NO3 and the excited states of NO3+. I. Electronic spectrum. Journal of Chemical Physics. 2002;117(9):4361-4370
An Experimental and Density Functional Study of the Sb-C Bond Activation and Organo-Rh Bond Formation from the Spontaneous Decay of [RhCl3(SbPh3)3]
No full textThe reaction of RhCl3 with SbPh3 that produces mer-[RhCl3(SbPh3)3] 1 and trans,mer-[RhCl2(Ph)(SbPh3)3] 2 [A. Cavaglioni, R. Cini, J. Chem. Soc., Dalton Trans. (1997) 1149 (and references cited therein)], as well as the transformation of 1 to 2, was studied in details using the UV-Vis spectroscopy and density functional approaches. We elucidated the mechanism of Sb-C(Ph) bond activation and Rh-C(Ph) bond formation during these processes. Experimental studies show that the first step of the reaction of RhCl3 with SbPh3 is the formation of 1, which later rearranges to complex 2 via a concerted mechanism. The transition state associated with this transformation includes the Rh(III) center (hepta-coordinate) that interacts with three Cl- ligands, two Sb-centers of SbPh3 ligands, and one Sb-Ph bond of the third SbPh3 ligand. The Cl- ligand, trans to Sb, bridges Rh and Sb atom from the third SbPh3 ligand. A possible pathway involving rhodium(I) intermediate species was also taken into account. The calculated geometry parameters of models of complexes 1 and 2 are in good agreement with the available X-ray data. Presented relative energies of the studied reactions are in good agreement with the relative yields of 1 and 2
A detailed study on the symmetry breaking and its effect on the potential surface of NO3
No full textEisfeld W, Morokuma K. A detailed study on the symmetry breaking and its effect on the potential surface of NO3. The Journal of Chemical Physics. 2000;113(14):5587-5597
The ONIOM-PCM method: Combining the hybrid molecular orbital method and the polarizable continuum model for solvation. Application to the geometry and properties of a merocyanine in solution
No full textWe present the ONIOM-PCM method, which combines the ONIOM (our own n-layered integrated molecular orbital+molecular mechanics) method with the polarizable continuum model (PCM). Four versions of the method have been developed. These schemes differ mainly with respect to the level of coupling between the solute charge distribution and the continuum, which has important consequences for the computational efficiency. Any property that can be calculated by both ONIOM and PCM can also be calculated by the ONIOM-PCM method. In the current paper we use this aspect for the calculation of the derivatives of the energy with respect to the nuclear coordinates to perform geometry optimizations, and the calculation of the nuclear magnetic resonance shielding for solvated molecules. To assess the various versions of the method, we performed ONIOM(B3LYP:Hartree–Fock)-PCM calculations on a merocyanine, H2N(C2H2)3CHO. All four schemes yield results close to the target B3LYP (three-parameter Becke–Lee–Yang–Parr density functional)-PCM, and the method appears to be a promising tool for accurate calculations on large molecules in solution
Quasiclassical Trajectory Studies of the Photodissociation Dynamics of NO<sub>3</sub> from the D<sub>0</sub> and D<sub>1</sub> Potential Energy Surfaces
No full textWe report new global potential energy surfaces (PESs)
for the D0 and D1 states of NO3.
The PESs are
permutationally invariant fits to roughly 90 000 electronic energies
(MS-CAS(17e,13o)PT2/aug-cc-pVTZ). Hundreds of thousands of quasiclassical
trajectories are run from the D0 global minimum and one
previously identified “roaming saddle point” as well
as a roaming saddle point on D1, identified previously
[Xiao, H.; Maeda, S.; Morokuma, K. J. Chem. Theory Comput. 2012, 8, 2600]. The calculations
are done at a total energy of relevance to recent experiments where,
together with theoretical analysis [Grubb, M. P.; Warter, M. L.; Xiao,
H.; Maeda, S.; Morokuma, K.; North, S. W. Science 2012, 335, 1075], point to roaming
pathways to the O2+NO products on both D1 and
D0. Detailed comparisons with experiment are made for the
distributions of O2 vibrational and rotational states,
the relative translational energy and the NO rotational states, and
the NO v-j vector correlation
Theoretical study of the SN2 reaction of Cl-(H2O)+CH3Cl using our own N-layered integral molecular orbital and molecular mechanics polarizable continuum model method (ONIOM-PCM)
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