Counterpoise corrections

Counterpoise correction should, in theory, be unnecessary for large basis... 

The counterpoise corrected complexation energy is given as A eompLexaUan — AEcp- For regular basis sets this typically stabilizes at the basis set limiting value much earlier than the uncorrected value, but this is not necessarily the case if diffuse functions are included in tlie basis set. 

Table 12-4. Computed interaction energy (AE) and counterpoise-corrected interaction energies (AECP) of the water dimer [kcal/mol]. The BSSE is given in parentheses.

Table 12-8. Deviation of counterpoise-corrected interaction energies [kcal/mol] for several hydrogen bonded systems from best available computed data (TZ2P basis set quality, all data from Tuma, Boese, and Handy, 1999). 

Hobza, P., Bludsky, O. Suhai, S., 1999, Reliable Theoretical Treatment of Molecular Clusters Counterpoise-Corrected Potential Energy Surface and Anharmonic Vibrational Frequencies of the Water Dimer , Phys. Chem. Chem. Phys., 1, 3073. 

The corrections for basis set superposition errors (BSSE) with the counterpoise correction are still a controversial issue [120-122], However, some type of correction is needed for calculations on systems with weak interactions. It has been proved that only considering the BSSE meaningful results can be obtained on large systems [122], Of course, by using good quality basis sets the BSSE is less troublesome and the results obtained can be accepted, readily, as reliable. The BSSE in DFT calculations is less important than in conventional ab-initio calculations. We compute the counterpoise correction as ... 

Derived from fits to the counterpoise-corrected interaction energies. 

Several methods have been suggested to estimate the BSSE and to correct Equation (1). The widely utilized full counterpoise correction suggests the computation of the interaction energy as the difference of the dimer (AB)... 

The ability to use precisely the same basis set parameters in the relativistic and non-relativistic calculations means that the basis set truncation error in either calculation cancels, to an excellent approximation, when we calculate the relativistic energy correction by taking the difference. The cancellation is not exact, because the relativistic calculation contains additional symmetry-types in the small component basis set, but the small-component overlap density of molecular spinors involving basis functions whose origin of coordinates are located at different centres is so small as to be negligible. The non-relativistic molecular structure calculation is, for all practical purposes, a precise counterpoise correction to the four-component relativistic molecular... 

The term BSSE was first introduced in 1973 by Liu and McLean (Liu and McLean, 1973). However, as early as 1970 Boys and Bernard (Boys and Bernard , 1970) had proposed the function counterpoise procedure (CP) as a strategy to correct for BSSE. In this procedure the monomer calculations are given the same flexibility that is available to the monomers in the dimer calculation, namely, the monomer energies are evaluated in the complete dimer basis set. The counterpoise-corrected interaction energy then becomes ... 

A counterpoise-corrected geometry optimization (with concurrent optimization of the intramolecular geometry) requires minimization of Eq. (5). To date, no automated counterpoise-corrected optimization algorithms based on Eq. (5) have... 

We first consider two very weakly bound molecules, He2 and Ar2, for which BSSE is a well recognized problem and then consider the impact of the counterpoise correction on the strongly bound N2, HF, and HCl molecules. 

Fig. 1. Counterpoise-corrected and uncorrected for the helium dimer. The dashed lines represent the estimated CBS limit.

Dg, Rg. and cOg for the argon dimer (van Mourik and Dunning Jr., to be published) are plotted in Figure 4. The results are similar to the corresponding He2 curves (see Figures 1 and 3), although there are now easily recognized oscillations in the uncorrected results. As in He2, the counterpoise-corrected curves are well behaved and can be used to establish the CBS limit with some confidence. 

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