J. Phys. Chem. 1992,96,6105
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correction provides a formal solution to the elimination of such an inconsistency. As has been stated, the BSSE is an unfortunate name since it is not an error associated with the basis set used. There is no reason for a complete basis set of an atom that all the basis functions must be centered on the single atomic Center Sir: We have performed some additional calculations on the N q as required by BSSE = 0. In most cases the apparent BSSE values potential using the larger basis sets formed by adding a few more can be changed in manipulation by several-fold or even an order sets of sp functions to the basis set 6-31 l+G(4d3f) or 6-311+Gof magnitude, while the corresponding interaction energy after (3d2f) (see later discussions). The results show that after CP correction is in the correct range as expected for the basis counterpoise (CP) correction the SCF interaction energy UHF ~et.69’9~ Therefore, the ultimate criterion for judging the reliability at R 3.2 A was underestimated by -5 phartrees and at 3.1 of a calculatioa is tb stability of the calculated interaction energy A by 3 phartrees for the 6-311+G(4d3f) basis set’ while the with the increase of the basis set. Apparently, the consistency was stabilized to the increast correlation interaction energy R@ of our results with those of Eggenberger et al. confirms that our of basis set. The total interaction energy AE“ from these new are within calculations are reliable (the small deviations in hEHF calculations thus agrees with that of Eggenberger et aLz*’ the allowed uncertainty). Meantime, the CP corrections are reduced by a factor of 2. These It should be mentioned that at least one set of d and one set calculations, together with those of Eggenberger, provide sufficient of f functions with the largest exponents in 6-3 1 1+G(4d3f) can evidence that the results and conclusions in our original paper’ be dropped without apparent loss of accuracy for the results exccpt are generally reliable and valid. The following is our detailed reply for the highly repulsive region (R < 2.5 A) of the potential. This to the comment on our work’ from Eggenberger et al. means that our basis set may be equivalent to 10s6p3d2f since First of all, one should keep in mind that the extreme accuracy 6-311G is roughly equivalent to 9sSp.’O Consequently, our basis (-99%) of the calculated interaction energy is never possible with set is fully balanced, not ‘overpolarized”. any basis set of the spdf quality and at the theoretical level of MP2 Registry No. Neon dimer, 12185-05-6. or even MP4 approximation. Our aim was to reach the accuracy of 90%. The sp functions in the 6-3 11+G(4d3f‘) basis set, although References aod Notes not fully saturated (this has been discussed in our paper), are of (1) Tao, F.-M.; Pan, Y.-K. J. Phys. Chem. 1991, 95, 9811. comparable quality to the overall basis set and to the theoretical (2) Eggenberger, R.; Gerber, S.; Huber, H.; Searles, D.Chem. Phys. 1991, approach. Such a basis set, the energy-optimized 6-31 1G set 156, 395. (3) Eggenberger, R.; Gerber, S.; Huber, H.;Searles,D. Chem. Phys. Leu. augmented with appropriate diffuse sp functions and polarization 1991, 183, 223. functions, has been recommended in the literature4.$for inter(4) van Lenthe, J. H.;van Duijneveldt-van de Rijdt, J. G. C. M.; van mediate quality intermolecular energy calculations. Our calcuDuijneveldt, F. B. Adu. Chem. Phys. 1987, 69, 521. (5) Hobza, P.; Zahradnik, R. Chem. Reu. 1988,88, 871. lations have in fact conihned the validity of such a basis set. The (6) Tao, F.-M.; Pan, Y.-K. J . Phys. Chem. 1991, 95, 3582. basis sets formed from the Huzinaga’s large sp set produce nearly (7) Tao, F.-M.; Pan, Y.-K. J. Phys. Chem., in press. the same results, as demonstrated by Eggenberger’s calculations. (8) Yang, J.; Kestner, N. R. J . Phys. Chem. 1991, 95,9214. The only benefits appear to be the smaller BSSE and the slightly (9) Tao, F.-M.; Klemperer, W. To be published. For Nez, since the attractive interaction energy better UHF. (10) See p 541 in ref 4. ‘Current address: Department of Chemistry, Brown University, Proviis comes dominantly from &OR, the high accuracy for UHF dence, RI 02912. only of secondary importance. The validity of the CP correction has been confirmed by more Department of Chemistry Fu-Ming Taot recent studies.&* It is almost ‘exact”, and the remaining error Boston College Yuh-Kang Pan* is much less than 1% in most cases.8 The BSSE should be inChestnut Hill, Massachusetts 02167 terpreted as the consequence from the use of inconsistent basis sets for the monomer and the dimer energy calculations. The CP Received: April 2, I992
Reply to the Comment on “Mraller-Plesset Perturbatlve ab Inltlo Cakulatlono of the Ne2 Potentlal”
0022-3654/92/2096-6105$03.00/0
0 1992 American Chemical Society
