Atom-bond electronegativity equalization method fused into molecular mechanics. I. A seven-site fluctuating charge and flexible body water potential function for water clusters

Abstract

Recently, experimental and theoretical studies on the water system are very active and noticeable. A transferable intermolecular potential seven points approach including fluctuation charges and flexible body (ABEEM-7P) based on a combination of the atom-bond electronegativity equalization and molecular mechanics (ABEEM/MM), and its application to small water clusters are explored and tested in this paper. The consistent combination of ABEEM and molecular mechanics (MM) is to take the ABEEM charges of atoms, bonds, and lone-pair electrons into the intermolecular electrostatic interaction term in molecular mechanics. To examine the charge transfer we have used two models coming from the charge constraint types: one is a charge neutrality constraint on whole water system and the other is on each water molecule. Compared with previous water force fields, the ABEEM-7P model has two characters: (1) the ABEEM-7P model not only presents the electrostatic interaction of atoms, bonds and lone-pair electrons and their changing in respond to different ambient environment but also introduces "the hydrogen bond interaction region" in which a new parameter k(lp,H)(R(lp,H)) is used to describe the electrostatic interaction of the lone-pair electron and the hydrogen atom which can form the hydrogen bond; (2) nonrigid but flexible water body permitting the vibration of the bond length and angle is allowed due to the combination of ABEEM and molecular mechanics, and for van der Waals interaction the ABEEM-7P model takes an all atom-atom interaction, i.e., oxygen-oxygen, hydrogen-hydrogen, oxygen-hydrogen interaction into account. The ABEEM-7P model based on ABEEM/MM gives quite accurate predictions for gas-phase state properties of the small water clusters (H(2)O)(n) (n=2-6), such as optimized geometries, monomer dipole moments, vibrational frequencies, and cluster interaction energies. Due to its explicit description of charges and the hydrogen bond, the ABEEM-7P model will be applied to discuss properties of liquid water, ice, aqueous solutions, and biological systems.

Mg2+/Ca2+ binding to DNA bases: a quantum chemical method and ABEEMσπ/MM fluctuating charge model study

“…In order to effectively describe the hydrogen bond interaction, which is quite different from the common electrostatic interactions, we introduce a new parameter k(R ij ) in the hydrogen bond interaction region [72][73][74]. k(R ij ) is dependent on the distance of metal cation and lone-pair electron, R ij , in the present study (Eq.…”

“…Meanwhile, although the QM region polarizes in response to the MM partial charges, the reverse is not also true (although fully polarizable QM/MM methods are being developed). Based on the atom-bond electronegativity equalization method (ABEEM) [69][70][71] fused into MM, Yang et al [72][73][74] have established a new generation of polarization molecular force field, that is, the ABEEMrp/MM fluctuating charge model. It has been applied successfully to the water system [72,73], ion solvation [75][76][77], organic molecules [78], peptides [79], and nucleic acid [74,75].…”

Molecular dynamics simulations of LiCl association and NaCl association in water by means of ABEEM/MM

“…The atom-bond electronegativity equalization method (ABEEM) has been designed and applied successfully to calculating the energy, charge distribution, etc., of a large organic or biological molecule [39][40][41][42] . Recently, ABEEM has been fused into MM, i.e., ABEEM/MM, which has been applied to the water and ion/water systems [28][29][30][31][32][33][34] . The total energy of a system consisting of an ion pair and many water molecules is given in Eq.…”

“…The electrostatic interactions between all charge sites are calculated using ABEEM charges [39][40][41][42] . The ABEEM/MM parameters have been tested in water and ion/water clusters as well as in liquid water and aqueous ionic solutions [28][29][30][31][32][33][34] , for example, the opti- , and so on. The ABEEM/MM parameters are summarized in Table 1.…”

“…In the present work, we use the constrained molecular dynamics simulations in terms of the ABEEM-7P water model [28][29][30][31] to calculate the mean force and the PMF for the LiCl and NaCl ion pairs. The present simulations differ from previous treatments in the following respects.…”