Density Functional Theory Study of NO Adsorbed in A-Zeolite

Abstract

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, ^(14)N hyperfine coupling tensors, and ^(23)Na 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 Å.

Additional details