Screened Electrostatically Embedded Many-Body Method

Abstract

The electrostatically embedded many-body (EE-MB) method has been very successful for calculating energies of molecular clusters. Here, we introduce screened charges in the EE-MB method and evaluate the accuracy of the resulting method for calculating the binding energy for five water hexamers. The screened EE-MB method shows dramatic improvement over the unscreened method. The mean unsigned deviation of the screened EE-MB binding energies relative to unfragmented calculations on the entire cluster is 0.60 kcal/mol at the pairwise additive (PA) level of approximation and 0.24 kcal/mol at the three-body (3B) level, as compared to mean unsigned deviations of 1.32 (PA) and 0.54 (3B) kcal/mol with unscreened charges. The mean unsigned percentage deviations with screened embedding are only 1.1% (PA) and 0.5% (3B). The high accuracy obtained with the very affordable and quadratically scaling PA method is very encouraging and opens the door to more accurate simulations on complex systems.

Fragment-based quantum mechanical methods for periodic systems with Ewald summation and mean image charge convention for long-range electrostatic interactions

“…There are a number of similar strategies, including the fragment molecular orbital (FMO) method 41,42 and the electrostatically embedded many-body (EE-MB) expansion method. [43][44][45][46] The double SCF procedure used in the FMO model 41,42 is identical to that developed in the earlier X-Pol method, 1-3 whereas two-body or three-body exchange and charge transfer corrections are added in the FMO2 or FMO3 implementation. 39 Although fragment-based methods have been applied to large systems, it appears that none of the previous biological applications have included long-range electrostatic effects.…”

Optimization of the explicit polarization (X-Pol) potential using a hybrid density functional

“…For carboxylic acid systems, both the syn and anti conformations are considered (26)(27)(28)(29)(30)(31)(32)(33). We note that the carboxylic acids are particularly good hydrogen bond donors, with computed binding energies of 7.6 and 8.4 kcal/mol for the syn (28) and anti (33) conformations of acetic acid using XP@B3LYP/6-31G(d), which may be compared with the reference values of 7.9 and 8.2 kcal/mol.…”

“…The interaction energies on the carbonyl sites are of similar magnitude as those found in aldehyde and ketone complexes. The hydrogen bond accepting ability of the hydroxyl oxygen is relatively weak (3.3 kcal/mol) in the syn (29) configuration, while the structure in the anti conformer (32) enjoys a secondary hydrogen bonding interaction [45] to the carbonyl oxygen, increasing the XP@B3LYP-binding energy to 5.6 kcal/mol. The latter is 0.9 kcal/mol greater than the reference energy.…”

“…The key to achieve fast convergence in this method, in contrast to early schemes [24], is to optimize the monomer, dimer and many-body fragmental molecular orbitals in the presence of all other fragments, rather than using isolated gas-phase fragment terms. There are a number of applications of this strategy, including the fragment molecular orbital (FMO) method [25,26] and the electrostatically embedded many-body (EE-MB) expansion method [27][28][29][30]. The SCF procedure used in the FMO model is identical to that developed in the X-Pol method [25,26], whereas two-body and three-body exchange and charge transfer effects are included in the FMO2 and FMO3 implementations [23].…”

Dependence of the Many-Body Interaction Strength in Water Clusters (H₂O)_<i>n</i> on the Water-Water Distance

“…CCSD(T)方法结合不同基组对水团簇中的多体效应进行了研究 [1][2][3][4][5][6][7][8][9][10][11][12][14][15][16][17][18][19][20] Xantheas 1 使用包含基组重叠误差 (BSSE)校正的MP2/aug-cc-pVTZ方法研究了(H 2 O) 3 中的二体和三体效应, 使用包含BSSE校正的 MP2/aug-cc-pVDZ方法, 研究了(H 2 O) n (n = 4-6)中的 多体效应, 1,2 发现三体作用在总作用能中所占比例 高达20%以上, 而四体和更高阶作用可以忽略.…”