Analytical gradients Atomic charges

H. P. Hratchian, P. V. Parandekar, K. Raghavachari, M. J. Frisch and T. Vreven, QM QM electronic embedding using Mulliken atomic charges. Energies and analytic gradients in an ONIOM framework submitted. 

Ab-initio methods, 1 Analytical gradients (PCM-LRCC), 42 Apparent charges operator, 4, 9 Apparent surface charges (ASC), 3 Apparent surface charges method (ASC), viii Atomic orbitals (AO), 6... 

The assumption for Eq. (1) is that the ELSD peak area is directly proportional to mass. For compounds of widely varying structures, charges, or vapor pressure, or for varying mobile phase compositions (e.g., gradient HPLC), the ELSD response can vary markedly (16-22). Thus, Eq. (1) is limited in its applicability. Similarly, mass spectral (MS) detectors are universal, but the response per unit weight depends greatly on the ionization type (e.g., electrospray, fast-atom bombardment, etc.) and on the ionization efficiency of the analyte. Refractive index is another universal detector, but it too suffers from variability in response depending on the mobile phase... 

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