CAJ | 학술논문

我们对 L-苯丙氨酸进行了全势能面搜索，采用 B3LYP 方法优化了 L-苯丙氨酸的648种可能构象，最终得到了37种稳定存在的构象。分别采用B3LYP、B3PW91、M06-2X、MP2和CCSD(T)计算了L-苯丙氨酸最稳定的10种构象的相对能量，其中M06-2X和MP2方法能够给出较好的结果。对比不同的基组，说明采用 aug-cc-pVDZ已经接近达到基组收敛极限。用电子传播子理论P3近似方法计算稳定构象外价壳层轨道的垂直电离能与光电子能谱实验符合的很好；根据构象的相对能量以及理论模拟与实验的光电能谱的比对，说明对气相光电子能谱至少四种构象有贡献。
아문대 L-분병안산진행료전세능면수색，채용 B3LYP 방법우화료 L-분병안산적648충가능구상，최종득도료37충은정존재적구상。분별채용B3LYP、B3PW91、M06-2X、MP2화CCSD(T)계산료L-분병안산최은정적10충구상적상대능량，기중M06-2X화MP2방법능구급출교호적결과。대비불동적기조，설명채용 aug-cc-pVDZ이경접근체도기조수렴겁한。용전자전파자이론P3근사방법계산은정구상외개각층궤도적수직전리능여광전자능보실험부합적흔호；근거구상적상대능량이급이론모의여실험적광전능보적비대，설명대기상광전자능보지소사충구상유공헌。
The full potential energy surface of L-phenylalanine has been searched.A total of 648 unique trial structures were generated by allowing for all combinations of internal single-bond rotamers and were optimized at the DFT/B3LYP level of theory.A total of 37 local minima conformers were found. The relative energies of ten low-lying conformations are carried out with five different methods:B3LYP, B3PW91,M06-2X,MP2 and CCSD(T).Comparing the relative energies of different methods,we find M06-2X and MP2 can predict a good result.Comparing the relative energies of different basis sets,one can draw a conclusion that the aug-cc-pVDZ basis set is high enough to give a convergent result.The vertical ionization energies of the conformers calculated with electron propagator theory P3/aug-cc-pVDZ are in good agreement with the experimental data from photoelectron spectroscopy.The relative energies of the conformations and the comparison between the simulated and experimental photoelectron spectra show that there are at least four conformations of phenylalanine in the gas-phase experiment.