Measurement and ab initio modeling of the inelastic neutron scattering of solid N-methylformamide
Measurement and ab initio modeling of the inelastic neutron scattering of solid N-methylformamide
复制标题
固体 N-甲基甲酰胺非弹性中子散射的测量和从头开始建模
DOI：
10.1063/1.475382
复制
发表时间：
1998
影响因子：
4.4
通讯作者：
F. Trouw
中科院分区：
文献类型：
--
作者：
P. Bouř;C. N. Tam;J. Sopková;F. Trouw
用非弹性中子散射（INS）技术研究了固体N-甲基甲酰胺（NMF）及其N-氘代类似物在15 K时的振动。用于获得晶体的正常振动模式的力场是基于量子化学计算和随后将较小的五聚体片段的谐波力场转移到11个NMF分子的片段。结晶NMF中存在的两种类型的氢键也用二聚体建模。不同的键合导致光谱中N-氢摆动模式的分裂。虽然氢键对振动频率有着深远的影响，但结果表明，以前提出的键合氢的双阱势的发生是不可能的。相反，观察到晶体NMF中沿着氢键的有限电子共轭沿着。与以前的模型不同，我们分别模拟了每个振动跃迁的相对INS强度，这导致了一个实质性的改善。
Vibrational motions of solid N-methylformamide (NMF) and its N-deuterated analogue are investigated using the inelastic neutron scattering (INS) technique at 15 K. The force field for obtaining the normal vibrational modes of the crystal is based on a quantum chemical calculation and a subsequent transfer of a harmonic force field of a smaller pentameric segment to a fragment of 11 NMF molecules. Two types of hydrogen bonds present in crystalline NMF are also modeled with dimers. The distinct bonding leads to a splitting of the N-hydrogen wagging mode in the spectrum. Although the hydrogen bonding has a profound effect on vibrational frequencies, the results indicate that an occurrence of a double-well potential for bonded hydrogen proposed previously is unlikely. Instead, a limited electronic conjugation along the hydrogen bonds in crystalline NMF is observed. Unlike in previous models, we simulate the relative INS intensity of each vibrational transition separately, which leads to a substantial improvem...