应用ABEEM方法计算烷烃的分子能量

Calculation of the alkane molecular energies in terms of ABEEM

将分子力场中的能量项加入到原子-键电负性均衡方法(ABEEM)的能量表达式中,获得了计算烷烃分子能量的方法.选取13个简单烷烃分子CnH2n+2(n=1～6)作为模型分子,调节分子中不同类型的碳和氢原子的价态能量参数.应用这些价态能量参数计算了55个烷烃分子CnH2n+2(n=7～12)的能量.所计算的能量与用MP2/6-311+G(d,p)方法下得到的68个烷烃分子能量相比较,它们的绝对偏差在0.0004～2kcal/mol之间,相对偏差在0.0058×10-6%～9.9795×10-6%之间.也可以计算直链烷烃分子CnH2n+2(n=4～6)不同构象的分子能量和构象能,ABEEM方法可以很好的重复MP2方法的结果.验证了利用ABEEM方法计算分子能量是精确的和可靠的,参数具有一定的可转移性和一致性.另外,使用该方法能非常快速地计算分子能量.使用MP2方法计算正十二烷的能量,需要4334s,而使用ABEEM方法仅用0.1093s,计算速度比MP2方法大约快4万倍.ABEEM方法能精确和快速地计算分子能量,为计算其他分子能量,如二肽,多肽等有机生物分子提供了1种方法.

Using the combination of energies of the molecular Force Field and atom-bond Electronegalitivity equalization method, the expression of alkane molecular energy has been proposed. In this paper, the 13 alkanes, CnH2n（n=1-6）, were chosen as the model molecules. The energy parameters have been calibrated to fit the MP2/6-311＋G（d,p） energy for the various types of C and H atoms. Using the parameters of the valence-state energy, the energies of 55 alkanes molecules, C. H2. （n= 7- 12）, were obtained. Compared with the energies calculated by MP2/6-311 ＋G（d, p）, the absolute derivation between 0. 0004 and 2 kcal/mol and the relative deviation between 0. 0058 × 10^-6% and 9. 9795 × 10^-6% for 68 alkanes. The molecular energies and conformational energies for the unbranched alkanes, Cn H2n （n=4-6）, were also calculated. ABEEM＇ s energies are able to reproduce MP2 results quite well. It can be shown that it is precisive and reliable to calculate the molecular energy using ABEEM method. The parameters are transferable and consistently usable. Moreover, the energies were obtained very lastly by ABEEM method. For example, for calculating the energy of the unbranched 12-alkane, ABEEM costed 0. 1093s, whereas MP2 took 4334s. the former is faster about 40000 times than the latter. The molecular energies were precisely and fast calculated by using ABEEM method. It provides us a method of precisively and lastly calculating the other molecular energies, such as dipeptide, polypeptide and so on.