Quantum mechanics-guided molecular

Norrby, P.-O., Rasmussen, T., Haller, J., Strassner, T., Houk, K. N. Rationalizing the Stereoselectivity of Osmium Tetroxide Asymmetric Dihydroxylations with Transition State Modeling Using Quantum Mechanics-Guided Molecular Mechanics. J. Am. Chem. Soc. 1999, 121, 10186-10192. 

Q2MM Quantum mechanical guided molecular mechanics... 

The development of an ab initio quantum molecular dynamics method is guided by the need to overcome two main obstacles. First, one needs to develop an efficient, yet accurate, method for solving the electronic Schrodinger equation for both ground and excited electronic states. Second, the quantum mechanical character of the nuclear dynamics must be addressed. (This is necessary for the description of photochemical and tunneling processes.) This section provides a detailed discussion of the approaches we have taken to solve these two problems. 

Because atomic charge is not a quantum mechanical observable, we must use some indirect method to calculate these values. Moreover, since we lack experimental results to guide us, other methods of validating our assignments must be devised. Accurate reproduction of some observable, whether experimentally measured (dipole moment) or determined directly from the wavefunction (electrostatic potential, molecular moments, etc.), increases our confidence in the reliability of the assigned charges. 

Molecular electrostatic potential The molecular electrostatic potential (MEP) associated with a molecule arises from the distribution of electrical charges of the nuclei and electrons of a molecule. The MEP is quantum mechanically defined in terms of the spatial coordinates of the charges on the nuclei and the electronic density function p(r) of the molecule. As the MEP is the net result of the opposing effects of the nuclei and the electrons, electrophiles will be guided to the regions of a molecule where the MEP is most negative. The MEP is a useful quantity in the study of molecular recognition processes. 

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