Molecular dynamics simulations problems with standard

The principal benefit of molecular dynamics simulations derives from its atomic scale treatment the models produce a picture of the atomic structure, which may be visualised directly using current state of the art imaging techniques, such as video production. This, of course, is in addition to the calculation of the standard range of structural information, such radial distribution functions, which can be measured directly. The problem with these measurements, obtained from neutron or x-ray scattering studies, is that they are essentially one dimensional, because of the isotropic nature of glass. A full three dimensional reconstruction of the atomic structure is not possible, therefore, so recourse to modeling is somewhat essential. 

None of this can be detected by standard geometric criteria. First-principles simulations like CPMD allow for new wave-function-based descriptors [231] as the electronic structure is - in addition to the positions of all atomic nuclei involved -available on the fly . Of course, the above mentioned fundamental problem that the interaction energy is not an observable quantity is in first-principle simulations as apparent as in static calculations. However, the wavefunction naturally tracks all electronic changes in an aggregate. A wavefunction-based descriptor would also be helpful in traditional molecular dynamics because snapshots can be calculated with advanced static quantum chemical methods. 

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