Liu Ya-Jun, Lund Anders, Persson Petter, Lunell Sten
Department of Quantum Chemistry, Uppsala University, Box 518, S-751 20 Uppsala, Sweden.
J Phys Chem B. 2005 Apr 28;109(16):7948-51. doi: 10.1021/jp044198b.
Density functional theory was employed to investigate the adsorption site and hyperfine interactions of nitric oxide adsorbed in Na-LTA (previous name NaA) zeolite. Three different cluster models of increasing complexity were used to represent the zeolite network: (1) a six-membered ring terminated by hydrogen atoms with one sodium ion above the ring, (2) as model 1 with the addition of three sodium ions located at the centers of three imagined four-membered rings adjacent to the six-membered ring, and (3) as model 2 with the addition of the three four-membered rings adjacent to the six-membered ring. Calculations on the largest system (model 3) showed very good agreement with measured electronic Zeeman interaction couplings, 14N hyperfine coupling tensors, and 23Na hyperfine and nuclear quadruple coupling tensors of the S = 1/2 Na+...N-O adsorption complex when the position of the sodium ion was relaxed. The optimized geometry of the complex agreed nicely with that estimated experimentally, except for the Na-N distance, where the present results indicate that the distance deduced from previous ENDOR experiments may be underestimated by as much as 0.5 angstroms.
采用密度泛函理论研究一氧化氮在Na-LTA（曾用名NaA）沸石中的吸附位点及超精细相互作用。使用了三种复杂度递增的不同簇模型来表示沸石网络：（1）由氢原子终止的六元环，环上方有一个钠离子；（2）在模型1的基础上，在与六元环相邻的三个假想四元环的中心添加三个钠离子；（3）在模型2的基础上，添加与六元环相邻的三个四元环。对最大体系（模型3）的计算表明，当钠离子位置弛豫时，对于S = 1/2的Na⁺...N-O吸附配合物，计算得到的电子塞曼相互作用耦合、¹⁴N超精细耦合张量以及²³Na超精细和核四极耦合张量与测量值非常吻合。配合物的优化几何结构与实验估计值吻合良好，但Na-N距离除外，目前的结果表明，先前电子核双共振（ENDOR）实验推导的距离可能被低估了多达0.5埃。
