Bending molecular

Cao G, Chen X Buckling of single-walled carbon nanombes upon bending molecular dynamics simulations and finite element method, Phys Rev B 73(15) 2952—2961, 2006. 

This is a variation or change in the angle of a bond occuiring on the plane of the bond as indicated with the symbol 8. Figures 1.7 through 1.10 show bending molecular motions. 

Stiffness is often a critical property of a material that determines how much a component will deform in response to force (e.g., stretching, compression, or bending). Molecular modeling has been used to predict the stiffness and strength of polymer nanocomposites with different types of nanopartides, for example, carbon... 

The analogous coupling between the antisyimnetric stretch and bend is forbidden in the H2O Hamiltonian because of syimnetry.) The 2 1 resonance is known as a Femii resonance after its introduction [ ] in molecular spectroscopy. The 2 1 resonance is often very prominent in spectra, especially between stretch and bend modes, which often have approximate 2 1 frequency ratios. The 2 1 couplmg leaves unchanged as a poly ad number the sum ... 

It is also possible to measure microwave spectra of some more strongly bound Van der Waals complexes in a gas cell ratlier tlian a molecular beam. Indeed, tire first microwave studies on molecular clusters were of this type, on carboxylic acid dimers [jd]. The resolution tliat can be achieved is not as high as in a molecular beam, but bulk gas studies have tire advantage tliat vibrational satellites, due to pure rotational transitions in complexes witli intennolecular bending and stretching modes excited, can often be identified. The frequencies of tire vibrational satellites contain infonnation on how the vibrationally averaged stmcture changes in tire excited states, while their intensities allow tire vibrational frequencies to be estimated. 

In an atomic level simulation, the bond stretch vibrations are usually the fastest motions in the molecular dynamics of biomolecules, so the evolution of the stretch vibration is taken as the reference propagator with the smallest time step. The nonbonded interactions, including van der Waals and electrostatic forces, are the slowest varying interactions, and a much larger time-step may be used. The bending, torsion and hydrogen-bonding forces are treated as intermediate time-scale interactions. 

Intensive use of cross-terms is important in force fields designed to predict vibrational spectra, whereas for the calculation of molecular structure only a limited set of cross-terms was found to be necessary. For the above-mentioned example, the coupling of bond-stretching (f and / and angle-bending (B) within a water molecule (see Figure 7-1.3, top left) can be calculated according to Eq. (30). 

Terms in the energy expression that describe a single aspect of the molecular shape, such as bond stretching, angle bending, ring inversion, or torsional motion, are called valence terms. All force fields have at least one valence term and most have three or more. 

Arestraint (not to be confused with a Model Builder constraint) is a user-specified one-atom tether, two-atom stretch, three-atom bend, or four-atom torsional interaction to add to the list of molecular mechanics interactions computed for a molecule. These added interactions are treated no differently from any other stretch, bend, or torsion, except that they employ a quadratic functional form. They replace no interaction, only add to the computed interactions. 

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