Diabatic ordering of the normal model of a reaction complex along the reaction path has several advantages with regard to adiabatic ordering. The method is based on rotations of the vibrational normal modes at one point, s, of the reaction path to maximize overlap with the vibrational modes at a neighboring point. Global rotations precede the rotations of degenerate modes so that changes in the...

Anharmonic vibrational calculations can already be computationally demanding for relatively small molecules. The main bottlenecks lie in the construction of the potential energy surface and in the size of the excitation space in the vibrational configuration interaction (VCI) calculations. To address these challenges, we use localized-mode coordinates to construct potential energy surfaces and ...

Electronic and vibrational structures in the S(0) (1)A(1) and S(1) (1)A(1) states of jet-cooled phenanthrene-h(10) and phenanthrene-d(10) were analyzed by high-resolution spectroscopy using a tunable nanosecond pulsed laser. The normal vibrational energies and molecular structures were estimated by ab initio calculations with geometry optimization in order to carry out a normal-mode analysis of...

The vibrational energy relaxation of a selected vibrational mode in cytochrome c--a C-D stretch in the terminal methyl group of Met80--has been studied using equilibrium molecular dynamics simulation and normal mode analysis methods. As demonstrated in the pioneering work of Romesberg and co-workers, isotopic labeling of the C-H (to C-D) stretch in alkyl side chains shifts the stretching freque...

The normal-mode spectrum for the four-coordinated heme compound Fe(II) octaethylporphyrin, Fe(OEP), has been determined by refining force constants to the experimental Fe vibrational density of states measured with nuclear resonance vibrational spectroscopy (NRVS). Convergence of the calculated spectrum to the data was achieved by first imposing D4 symmetry on the model structure as well as the...

Employing extensive quantum-chemical calculations at the DFT/B3LYP and MP2 level, quartic force fields of isolated N-methylacetamide are constructed. Taking into account 24 vibrational degrees of freedom, the model is employed to perform numerically exact vibrational configuration interaction calculations of the vibrational energy relaxation of the amide I mode. It is found that the energy tran...

We have developed a computational approach that yields anharmonic vibrational couplings in molecular crystals. The approach is based on anharmonic vibrational potential-energy surface reconstruction starting from a normal-mode vibrational basis. The method was implemented for semiempirical Hamiltonians with periodic boundary conditions, with applications to crystalline naphthalene and pentaeryt...

The fundamental frequencies and mode shapes of steel and carbon fiber–reinforced plastic (CFRP) cylindrical shells with steel inserts were investigated using finite element analysis and modal testing. The free-free boundary condition was tested with modal testing using the roving hammer method and verified by finite element analysis using ABAQUS. The results show good agreement between the test...