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THE EFFECT OF THE NATURE OF THE INTERACTION POTENTIAL ON CLUSTER REACTION RATES

机译：相互作用电位的性质对簇反应速率的影响

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The effect of two different interaction potentials, a two-body potential, on thermal cluster reaction rates was studied for 2-13 atom nickel clusters using the classical trajectory method. The reaction rates were computed for cluster-monomer and cluster-cluster collisions at T = 1200 K, using the bulk and dimer parametrized Lennard-Jones (LJ) potentials and were compared with the rates previously obtained for these collisional events by using a more realistic many-body tight-binding second moment approximation (TB-SMA) potential. For cluster-monomer collisions, close agreement exists between the reaction cross section results for dimer fitted LJ (LJD) potential and TB-SMA potential suggesting that the cluster-monomer collisions may be dominated by pairwise interactions. The bulk fitted LJ potential (LJB) underestimates the sticking cross section results of the other two potentials for most cluster sizes. This discrepancy however appears to be due to the relatively smaller cluster binding energies obtained for this potential as a result of which a larger cross section for dissociation is observed. For cluster-cluster collisions, for most cluster sizes, no agreement exists between the reaction cross section results for the three potentials. The discrepancy between the cross section results for the LJ potentials and the TB-SMA potential appears to lie in the difference in the scaling of cluster energy with cluster coordination for these two types of potentials (i.e., linear for LJ vs square root dependence for TB-SMA). Some characteristics of the cross section results of both LJB and LJD potentials correlate with the relative cluster stability pattern for the LJ clusters. For TB-SMA case, no such correlation exists, which however is consistent with the smooth and featureless size distributions observed experimentally for nickel and other transition metals. The cut-off used in the TB-SMA potential appears to lead to a significant underestimation of the total reaction cross section for N = 13, in the case of the cluster-cluster collisions. The results of this study indicate that the rate calculations may be sensitive to both the nature and parameterization of the simulation potential depending on the temperature range considered and cluster growth process simulated. (C) 1996 American Institute of Physics. [References: 38]
机译：使用经典轨迹方法研究了2-13个原子镍团簇的两种不同的相互作用势（两体势）对热团簇反应速率的影响。使用本体和二聚体参数化的Lennard-Jones（LJ）电势，计算了T = 1200 K时簇-单体和簇-簇碰撞的反应速率，并通过更现实的方法将其与先前针对这些碰撞事件获得的速率进行了比较。多体紧结合的第二矩近似（TB-SMA）潜力。对于簇-单体碰撞，二聚体拟合的LJ（LJD）电位和TB-SMA电位的反应横截面结果之间存在密切的一致性，这表明簇-单体碰撞可能以成对相互作用为主。散装的LJ电位（LJB）低估了大多数簇尺寸的其他两个电位的粘滞横截面结果。然而，该差异似乎是由于为此电位获得的相对较小的簇结合能，其结果是观察到较大的离解截面。对于簇-簇碰撞，对于大多数簇尺寸，三个势的反应截面结果之间没有一致性。 LJ电位和TB-SMA电位的横截面结果之间的差异似乎在于，这两种类型的电位的簇协调作用下，簇能量的缩放比例存在差异（即，LJ的线性与TB的平方根依赖性） -SMA）。 LJB和LJD电位的横截面结果的某些特征与LJ簇的相对簇稳定性模式相关。对于TB-SMA情况，不存在这样的相关性，但这与对镍和其他过渡金属的实验观察到的平滑无特征的尺寸分布一致。在簇-簇碰撞的情况下，TB-SMA电位中使用的截止值似乎导致对总反应截面的N = 13的低估。这项研究的结果表明，速率计算可能对模拟电位的性质和参数化敏感，具体取决于所考虑的温度范围和模拟的簇生长过程。 （C）1996年美国物理研究所。 [参考：38]

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