High-level ab inito Calculation and Assessment of the Dissociation Ionization Energies of NH2 and NH3 Neutrals or Cations

doi:10.3866/PKU.WHXB19960501

	High-level ab inito Calculation and Assessment of the Dissociation Ionization Energies of NH2 and NH3 Neutrals or Cations
	Su Kehe 1; Wen Zhenyi 2; Hu Xiaoling 1; Li Xiuyi 1; Wang Yubin 2
刊名	ACTA PHYSICO-CHIMICA SINICA
	1996
卷号	12 页码:385-390
关键词	NH2 NH3 NH2+ NH3+ Dissociation Ionization Ab initio
ISSN号	1000-6818
DOI	10.3866/PKU.WHXB19960501
英文摘要	A recent experimental determination([1]) of the dissociation energies (D-0) for H2N-H, H2N+ = H and H2N-H+, the ionization energies for NH3 and NH2 resulted in large deviations when compared with those of the earlier values and the QCISD(T)/6-311+G(3df,2p) G(3df,2p) ab initio calculations. We have performed some higher level ab initio calculations on these data by utilizing the Gauss: 92/DFT and Gaussian 94 pakages of programs and have assessed the available experimental values. Our calculations were can out at the QCISD(TQ)/aug-cc-pVDZ, G2(QCI), QCISD(T) 6-311++G(3df,3pd) and QCISD(T) aug-cc-pVTZ levels of theory. Geometries were optimized at both of the MP2(full)/6-31G(d) and the MP2(full)/6-31(d,p) levels, and were compared with those of the experiments if available The MP2(full)/6-31G(d,p) tight-optimized geometries for the neutrals are closer to those of the experiments with those of the QCISD(T)(full) /6-31G(d), and are in excellent agreement with the experimental results as shown in Table 1. In this case, we assumed that the optimized geometries for the cations would be better if p polarization functions are added to the hydrogen atoms. We firstly noted that the symmetry of the cation was D-w, other than C-a, as reported in ref.[1]. All of the zero point energies and the final geometries are calculated at the MP2(full)/6-31G(d,p) level of theory_ We have also repeated the 6)(150(T)/6-311+G(3df,2p) calculations of ref.[1],, because we could not identify their level of goemetry optimization It is found that the total energy, -55.244 19 Hartrees, for NH2+ ((1)A(1)) in ref.[1] might be in error. Our result is -(55.336 29 Hartrees at the same level of theory. At our highest level ([QCISD(T)aug-cc-pVTZ] of calculations as shown in Table 3, the Do (temperature at zero Kelvin) values of H2N-H, H2N+-H(B-3(1) for NH2+ and H2N-H+ are 4.51, 5.49 and 8.00 eV, respectively. These data reported in ref.[1] were 4.97, 5.59 and 8.41 eV, respectively. Our result on D-0(H2N-H) supports the work of ref [2356] The ionization energies (IE) for NH3 and NH2 (B-3(1) for NH2+) at our highest level are 10.11 and 11.09 eV while in ref[1] were 10.16 and 10,78 eV, respectively. For the latter, our result supports the experiment of ref,[3].. Our predicted D0 for HN2+-H and IE for NH2 ((1)A(1) for each NI In are 6.80 and 12.39 eV, respectively. These values differ greatly from the predicted values (9.29 and 14.88 eV) of rein where the total energy of N-2(+)-((1)A(1)) might be in error. The D-0 value for HN-H has not been found in ref.[1]. Our result supports the work of ref.[3]. We have also derived all of these values at the temperature of 298K and under the pressure of 101kPa at several levels of thoery as shown in Table 3. On exmaning the experiment of ref.[1]. in detail, it is easy to find that all of the larger deviations might be from a too high value of the appearance potential of proton AP(H+). Indeed, ref.[1]. has mentioned that the determinition of AF(H+), due to kinetic shift, would lead to a hihger value for the dissociation energy as has been pointed out by Berkowitz nd Ruscic. in this work, concluded that, besides some mistakes in the theoretical calculations of ref.[1], the dissociatiion energies for H2N-H and H2N-H+, the IE for NH2 (B-3(1) for NH2+()) might also be unreliable and need to be re-examined.
WOS研究方向	Chemistry
语种	英语
出版者	PEKING UNIV PRESS
WOS记录号	WOS:000207599800001
内容类型	期刊论文
源URL	[http://119.78.100.186/handle/113462/35179]
专题	中国科学院近代物理研究所
通讯作者	Su Kehe
作者单位	1.NW Polytech Univ, Dept Chem Engn, Xian 710072, Shaanxi, Peoples R China 2.Northwest Univ, Inst Modern Phys, Xian 710069, Shanxi, Peoples R China
推荐引用方式 GB/T 7714	Su Kehe,Wen Zhenyi,Hu Xiaoling,et al. High-level ab inito Calculation and Assessment of the Dissociation Ionization Energies of NH2 and NH3 Neutrals or Cations[J]. ACTA PHYSICO-CHIMICA SINICA,1996,12:385-390.
APA	Su Kehe,Wen Zhenyi,Hu Xiaoling,Li Xiuyi,&Wang Yubin.(1996).High-level ab inito Calculation and Assessment of the Dissociation Ionization Energies of NH2 and NH3 Neutrals or Cations.ACTA PHYSICO-CHIMICA SINICA,12,385-390.
MLA	Su Kehe,et al."High-level ab inito Calculation and Assessment of the Dissociation Ionization Energies of NH2 and NH3 Neutrals or Cations".ACTA PHYSICO-CHIMICA SINICA 12(1996):385-390.