The importance of three-body terms in the fragment molecular orbital method
The importance of three-body terms in the fragment molecular orbital method
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DOI：
10.1063/1.1687334
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发表时间：
2004-04-15
影响因子：
4.4
通讯作者：
Kitaura, K
中科院分区：
文献类型：
--
作者：
Fedorov, DG;Kitaura, K
将一种基于限制性Hartree-Fock（RHF）方法的二体碎片分子轨道方法扩展到包含显式三体项。使用STO-3G、3- 21 G、6- 31 G和6-31++G** 基组，在一组代表性分子：（H2O）（n），n =16、32和64，以及丙氨酸的α和β n-mer，n=10、20和40上测试了该方法的准确度。两体和三体结果分别提供，用于分配每个片段的一个和两个分子（或残基）。发现总能量与常规RHF方法相差至多Δ E（2/1）=0.06，Δ E（2/2）=0.04，Δ E（3/1）=0.02，Δ E（3/2）=0.003（a.u.）; rms能量梯度相差最多DeltaG（2/1）=0.0015，DeltaG（2/2）=0.000 75，DeltaG（3/1）=0.000 20和DeltaG（3/2）=0.000 10（a.u./ bohr），并且rms偶极矩以至多Δ D（2/1）=3.7、Δ D（2/2）=3.4、Δ D（3/1）=2.6和Δ D（3/2）=3.1（%）的相对误差再现，其中下标符号n/m是指基于每个片段m个分子（残基）的n体方法。一些最大的三体计算是用分离的三聚体近似进行的，这大概会降低对密度分布的微小变化非常敏感的大部分偶极矩的准确性。所提出的方法是能够提供足够的化学准确性，同时提供详细的多体相互作用的信息。(C)2004年，美国物理学会。
A previously proposed two-body fragment molecular orbital method based on the restricted Hartree-Fock (RHF) method was extended to include explicit three-body terms. The accuracy of the method was tested on a set of representative molecules: (H2O)(n), n=16, 32, and 64, as well as alpha and beta n-mers of alanine, n=10, 20, and 40, using STO-3G, 3-21G, 6-31G, and 6-31++G** basis sets. Two- and three-body results are presented separately for assigning one and two molecules (or residues) per fragment. Total energies are found to differ from the regular RHF method by at most DeltaE(2/1)=0.06, DeltaE(2/2)=0.04, DeltaE(3/1)=0.02, and DeltaE(3/2)=0.003 (a.u.); rms energy gradients differ by at most DeltaG(2/1)=0.0015, DeltaG(2/2)=0.000 75, DeltaG(3/1)=0.000 20, and DeltaG(3/2)=0.000 10 (a.u./bohr), and rms dipole moments are reproduced with at most deltaD(2/1)=3.7, deltaD(2/2)=3.4, deltaD(3/1)=2.6, and deltaD(3/2)=3.1 (%) relative error, where the subscript notation n/m refers to the n-body method based on m molecules (residues) per fragment. A few of the largest three-body calculations were performed with a separated trimer approximation, which presumably somewhat lowered the accuracy of mostly dipole moments which are very sensitive to slight variations in the density distribution. The proposed method is capable of providing sufficient chemical accuracy while providing detailed information on many-body interactions. (C) 2004 American Institute of Physics.