| Research Abstract |
Ab initio dynamics are carried out as development of high-speed computers. Still this approach is still very CPU demanding if used with quantum chemical cal culations of sufficient quality to describe chemical reactions accurately. Thus, we developed an interpolation scheme using no derivatives in ab initio calculations. In this scheme, we combine interpolant moving least squares method and Shepard scheme (IMLS/Shepard). We applied the present scheme to O+ H_2, OH+H_2, H_2+ H_2 and Li+ H_2 systems. We also investigate the effect of Bayesian approach proposed by Bettens and Collins. In O+ Ha system, the best result of IMLS/Shepard scheme was shown to have similar magnitude of rms errors to that of Shepard scheme for the same number of interpolant points. Thus, IMLS/Shepard has great advantage in comparison with Shepard scheme because Shepard scheme requires up to second derivatives of potential energy surfaces. On the other hand, for the OH+ H_2 system, tighter weight functions than for O+ H_2 system was favorable as for all of rms, mean absolute, and median absolute errors. Bayesian approach improved IMLS/Shepard results in addition to Shepard results. Overall, we have showed the advantage of the present scheme, which does not require any derivatives in ab initio calculations.
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