Wheeler Steven E, Schaefer Henry F
Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA.
J Chem Phys. 2005 May 22;122(20):204328. doi: 10.1063/1.1906207.
We present accurate ionization potentials (IPs) for small lithium clusters and hydrogenated lithium clusters (n=1-4), computed using coupled-cluster singles and doubles theory augmented with a perturbative correction for connected triple excitations [CCSD(T)] with the correlation-consistent weighted core-valence quadruple-zeta basis set (cc-pwCVQZ). In some cases the full CCSDT method has been used. Comparison of computed binding energies with experiment for the pure cationic lithium clusters reveals excellent agreement, demonstrating that previous discrepancies between computed and experimentally derived atomization energies for the corresponding neutral clusters are due to the use of an inaccurate experimental IP for Li(4). The experimental IP for Li(4) falls 0.43 eV below our theoretical adiabatic value of 4.74 eV, which should be a lower bound to the measured IP. Our recommended zero-point corrected adiabatic IPs for Li, Li(2), Li(3), Li(4), LiH, Li(2)H, Li(3)H, and Li(4)H are 5.39, 5.14, 4.11, 4.74, 7.69, 3.98, 4.69, and 4.05 eV, respectively. Zero-point vibrationally corrected CCSD(T) atomization energies per atom for Li(2) (+), Li(3) (+), Li(4) (+), LiH(+), Li(2)H(+), Li(3)H(+), and Li(4)H(+) are 0.64, 0.96, 0.90, 0.056, 1.62, 1.40, and 1.40 eV, respectively.
我们给出了小锂簇和氢化锂簇（n = 1 - 4）的精确电离能（IPs），这些数据是使用耦合簇单双激发理论并辅以连接三激发的微扰校正[CCSD(T)]，结合相关一致加权核价四重ζ基组（cc-pwCVQZ）计算得出的。在某些情况下，使用了完整的CCSDT方法。将计算得到的纯阳离子锂簇的结合能与实验结果进行比较，结果显示出极佳的一致性，这表明之前计算得到的与通过实验得出的相应中性簇的原子化能之间的差异是由于使用了不准确的Li(4)实验电离能。Li(4)的实验电离能比我们理论绝热值4.74 eV低0.43 eV，该理论绝热值应是测量电离能的下限。我们推荐的经零点校正的Li、Li(2)、Li(3)、Li(4)、LiH、Li(2)H、Li(3)H和Li(4)H的绝热电离能分别为5.39、5.14、4.11、4.74、7.69、3.98、4.69和4.05 eV。Li(2)(+)、Li(3)(+)、Li(4)(+)、LiH(+)、Li(2)H(+)、Li(3)H(+)和Li(4)H(+)每个原子的经零点振动校正的CCSD(T)原子化能分别为0.64、0.96、0.90、0.056、1.62、1.40和1.40 eV。
