Counterpoise-corrected potential energy surfaces of simple H-bonded systems |
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Authors: | Pavel Hobza Zdenvk Havlas |
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Institution: | (1) J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-182 23 Prague, Czech Republic, XX;(2) Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, CZ-160 00 Prague, Czech Republic, XX |
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Abstract: | Geometries and stabilization energies of various simple H-bonded complexes (water dimer, hydrogen fluoride dimer, formamide
dimer, formic acid dimer) have been determined by a gradient optimization that eliminates the basis set superposition error
(BSSE) by the counterpoise (CP) method in each gradient cycle as well as by the standard gradient optimization. Both optimization
methods lead to different potential energy surfaces (PES). The difference depends on the theoretical level used and is larger
if correlation energy is considered. Intermolecular distances from the CP-corrected PES are consistently longer, and this
difference might be significant (∼0.1 ?); also angular characteristics determined from both surfaces differ significantly.
Different geometries were obtained even when passing to larger basis sets (aug-cc-pVDZ). The standard optimization procedure
can result in a completely wrong structure. For example, the “quasi-linear” structure of the (HF)2 (global minimum) does not exist at the standard MP2/ 6-31G** PES (where only cyclic structure was detected) and is found
only at the CP-corrected PES. Stabilization energies obtained from the CP-corrected PES are always larger than these from
the standard PES where the BSSE is added only a posteriori for the final optimized structure; both energies converge only
when passing to a larger basis set (aug-cc-pVDZ).
Received: 11 March 1998 / Accepted: 19 June 1998 / Published online: 4 September 1998
RID="
ID=" <E6>Acknowledgements.</E6> The project was supported by the Grant Agency of the Czech Republic (Grant No. 203/98/1166).
RID="
ID=" <E5>Correspondence to</E5>: P. Hobza |
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Keywords: | Counterpoise-corrected gradient optimization H-bonded systemsRID="ID=" < E6> Acknowledgements < /E6> The project was supported by the Grant Agency of the Czech Republic (Grant No 203/98/1166) RID="ID=" < E5> Correspondence to< /E5> : P Hobza |
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