Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander Universität Erlangen-Nürnberg, Nägelsbachstr. 25, 91052, Erlangen, Germany.
J Mol Model. 2010 Sep;16(9):1427-40. doi: 10.1007/s00894-010-0650-7. Epub 2010 Feb 17.
We describe an improved force field parameter set for the generalized AMBER force field (GAFF) for urea. Quantum chemical computations were used to obtain geometrical and energetic parameters of urea dimers and larger oligomers using AM1 semiempirical MO theory, density functional theory at the B3LYP/6-31G(d,p) level, MP2 and CCSD ab initio calculations with the 6-311++G(d,p), aug-cc-pVDZ, aug-cc-pVTZ, and aug-cc-pVQZ basis sets, and with the CBS-QB3 and CBS-APNO complete basis set methods. Seven different urea dimer structures were optimized at the MP2/aug-cc-pVDZ level to obtain accurate interaction energies. Atomic partial charges were calculated at the MP2/aug-cc-pVDZ level with the restrained electrostatic potential (RESP) fitting approach. The interaction energies computed with these new RESP charges in the force field are consistent with those obtained from CCSD and MP2 calculations. The linear dimer structure calculated using the force field with modified geometrical parameters and the new RESP charge set agrees well with available experimental data.
我们描述了一种改进的尿素广义 AMBER 力场（GAFF）力场参数集。使用 AM1 半经验 MO 理论、B3LYP/6-31G(d,p) 密度泛函理论、MP2 和 CCSD 从头算方法（使用 6-311++G(d,p)、aug-cc-pVDZ、aug-cc-pVTZ 和 aug-cc-pVQZ 基组）以及 CBS-QB3 和 CBS-APNO 完全基组方法，对尿素二聚体和更大的低聚物的几何形状和能量参数进行了量子化学计算。使用 MP2/aug-cc-pVDZ 水平优化了七种不同的尿素二聚体结构，以获得准确的相互作用能。使用受限静电势（RESP）拟合方法在 MP2/aug-cc-pVDZ 水平上计算原子部分电荷。用这些新的 RESP 电荷在力场中计算的相互作用能与 CCSD 和 MP2 计算得到的相互作用能一致。使用经过修改的几何参数和新的 RESP 电荷集的力场计算得到的线性二聚体结构与可用的实验数据吻合良好。
