Benzene geometry optimization

The potential surfaces of the ground and excited states in the vicinity of the conical intersection were calculated point by point, along the trajectory leading from the antiaromatic transition state to the benzene and H2 products. In this calculation, the HH distance was varied, and all other coordinates were optimized to obtain the minimum energy of the system in the excited electronic state ( Ai). The energy of the ground state was calculated at the geometry optimized for the excited state. In the calculation of the conical intersection... 

The final geometry optimizations with the DZ+D basis set and the analytic calculation of the force fields and MP-2 corrections were done with the program GRADSCfI on a CRAY-IA. There are 128 basis functions for the difluoro-benzenes, 132 basis functions for the dihydroxybenzenes and 136 basis functions for the diaminobenzenes. The calculations on the difluorobenzenes require about 14 x 10 non-zero 2e integrals whereas the calculations on the diaminobenzenes require about 40 x 10 non-zero 2e integrals. The integral sort step required for the... 

S. M. Mattar and S. E. Brewer,/. Phys. Chem., 96,1611 (1992). Geometry Optimization and Computation of the Electronic Structure of Benzene-Vanadium Molecules by the Local-Density-Functional LCAO Method. 

Table 8 Aromaticity (in %, benzene 100%, cyclopentadiene 0%) of different prototropic forms 7, 24,106,108, and 109 of 5-R-tetrazoles calculated from differences in bond orders (AN) based on geometry optimized at B3LYP/6-31G level <2004JMT(668)123>...

One of the first papers on EA applications to global cluster geometry optimization dealt with benzene clusters [17]. This system was used again by Pullan [39] in the development period, for n<15. A recent reinvestigation by Cai et al. [107] only went up to n=7, reproducing known results. 

Once the structmes of the two species were obtained, calculations were carried out for a pair of vinylcarbene molecules on the model surface starting from both HH-TT and HT-TH orientations (H and T refer to head and tail, respectively). The geometry optimizations led to 1,4- and 1,3-cyclohexadiene, which are indeed the intermediates suggested by Middleton and Lambert. These intermediates are stable with respect to dissociation to gas-phase benzene plus hydrogen by about 0.5 eV. Thus the energy cost is relatively low and the reaction may be expected to occur but, in agreement... 

The polarizable continuum model (PCM) by Tomasi and coworkers [77-79] was selected to describe the effects of solvent, because it was used to successfully investigate the effect of solvent upon the energetics and equilibria of other small molecular systems. The PCM method has been described in detail [80]. The solvents and dielectric constants used were benzene (s = 2.25), methylene chloride (g = 8.93), methanol (g = 32.0), and water (g = 78.4). Full geometry optimizations were carried out for the discrete and PCM models. To simultaneously account for localized hydrogen bonding and bulk solvation effects, PCM single-point energy calculations have been conducted on stationary points of the acrolein and butadiene reaction with two waters explicitly... 

Using a CNDO/2 model the energies for adding H+ and H io la have been calculated No geometry optimization of these reaction products was made. Therefore these results have also a more or less qualitative character. It is found that the 3 position can be seen to be the preferred position for electrophilic attack. It is predicted that it wiU take place as facile as with benzene. 

Test calculations were performed for three molecules, cyclopropane, benzene, and adamantane. First, we performed geometry optimization of the three molecules by Hartree-Fock calculations with a valence double-zeta basis set with a single set of polarization functions [28]. This was done with the purpose to save expansion coefficients of occupied molecular orbitals for a subsequent evaluation of A terms [Eq. (15)] and for calculation of differential cross sections. Details of our scattering calculations have been... 

Lee and Kertesz [50] used MNDO for geometry optimization and Hiickel theory for band structure calculations and applied them separately to the aromatic and quinonoid forms of poly thiophene (12) and derivatives with fused benzene 1, naphthalene 16, and anthracene 18 rings. The band gaps for the quinonoid and aromatic... 

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