Potential derived atomic charges

K. M. Merz Jr., J. Comput. Chem., 13, 749 (1992). Analysis of a Large Data Base of Electrostatic Potential Derived Atomic Charges. 

The issue of transferability of atomic charge models between conformations has been more vigorously discussed in the last decade. Most force fields assume that the charge distribution associated with each atom is independent of conformation. However, it has been noted that potential derived atomic charges do vary with the conformation of the molecule used to derive them and that these variations have a significant effect on computed properties such as the free energy of hydration of alcohols. 

MEP, molecular electronic potential SMEP(X), sum of the electrostatic potential-derived atomic charges on atom X Mean, average MEP values Variance, variance of MEP values HBA, number of hydrogen-bond acceptors HBD, number of hydrogen-bond donors AR, number of aromatic rings and MW, molecular weight. 

The total computational effort involved in setting up the shell-pair data increases linearly with the size N of the basis. For tasks such as large Direct SCF calculations [44,45], it is entirely negligible compared with the subsequent work for less computationally demanding tasks, such as finding potential-derived atomic charges [98], it typically constitutes 10% of the job time. 

A class of improved population analysis schemes has been designed to reproduce the total dipole moment of the molecule when calculated by point charges. Such a dipole moment conserving procedure was proposed e.g. by Jug [99] and by Thole and van Duijnen [100]. A more general multipole fitted scheme has also been derived [101]. A slightly different approach is to determine potential derived atomic charges which are fitted to reproduce the values of the electrostatic potential outside the van der Waals envelope of the molecule [102, 103]. 

Stone s DMA method has been applied in several other papers. Our review cannot be exhaustive but we would like to quote two additional papers using this approach because they give additional information on the basic problems of the electrostatic approach. Price, Harrison and Guest [89] examined the DMA description of the MEP of a large molecule, with formula C63H113N11O12, obtained from a 3-21G SCF wavefunction. The description of the electrostatic potential obtained in such a way is comparable to that obtained with potential derived atomic charges (PD-AC) to which we shall refer later on in more detail. The superiority of a distribute multipole description, in describing the anisotropic contributions to the MEP on the van der Waals surface is shown clearly. 

Merz KM. Analysis of a large data base of eleetrostatie potential derived atomic charges. J ComputChem. 1992 13 749-67. 

Function e provides a critical test for the approximate charge distribution model related to real applications. As the first example, we used imidazole, which frequently models histidine residue. In the Table 3 we compare results obtained for four different molecular charge density models Mulliken [27], CHELP [28] and ESP [29] charges and CAMM (up to quadruples). In general, electrostatic potentials on solvent accessible surfaces described by CAMM series truncated at quadrupole term tend to perform slightly better s = 2-10% than those calculated using potential-derived atomic charges. 

Table 4 Summary of PESP Errors in Electrostatic Potential Derived Atomic Charges Relative to ab initio MP2/6-31G Values...

Z1, P Cieplak, W D Cornell and P A Kolhnan 1993. A Well-Behaved Electrostatic Potential Based 5thod for Deriving Atomic Charges - The RESP Model. Journal of Physical Chemistry 97 10269-10280. sen H C, J P M Postma, W F van Gunsteren and J Hermans 1981. Interaction Models for Water in lation to Protein Hydration. In Pullman B (Editor). Intermolecular Forces. Dordrecht, Reidel, I. 331-342. 

These results are given for the DNA bases in Table 4. The calculated effects are quite substantial, with the predicted increases in dipole moments essentially parallelling the magnitudes of the polarization energies. Given (p solute solution molecular electrostatic potentials can also be obtained in solution, and used to derive atomic charges.85,86... 

Sigfridsson, E. and Ryde U., Comparison of methods for deriving atomic charges from the electrostatic potential and moments. J.Comput.Chem. (1998) 19 377-395. 

Well-Behaved Electrostatic Potential Based Method Using Charge Restraints for Deriving Atomic Charges The RESP Model. 

Deriving Atomic Charges from the Electrostatic Potential and Moments. 

E. Sigfridsson and U. Ryde,/. Comput. Chem., 19, 377 (1998). Comparison of Methods for Deriving Atomic Charges from the Electrostatic Potential and Moments. 

Bayly, C. I. Cieplak, P. Cornell, W. D. Kollman, P. A., A well-behaved electrostatic potential based method using charge restraints for deriving atomic charges the RESP model,. /. Phys. Chem. 1993, 97, 10269-10280... 

We now discuss a recently developed method to derive atomic charges from WFCs [225]. This method is closely related to the D-RESP procedure of the Roethlisberger group [226]. We consider a molecule of M atoms with charges Za and atomic positions R. The electronic distribution of the molecule is described by n WFCs with charges — at positions r. has a value of one for the spin polarized case and a value of two for spin restricted calculations. The electrostatic potential of the molecule derived from the WFCs is defined as... 

Bayly C1, P Cieplak, W D Cornell and P A Kollman 1993. A Well-Behaved Electrostatic Potential Based Method for Deriving Atomic Charges - The RESP Model. Journal of Physical Chemistry 97 10269-10280. 

C. I. Bayly, P. Cieplak, W. D. Cornell, and P. A. Kollman, J. Phys. Chem., 97,10269 (1993). A Well-Behaved Electrostatic Potential Based Method Using Charge Restraints for Deriving Atomic Charges The RESP Model. 

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