Aug-cc-pVnZ

CCSD(T)/cc-pVnZ+aug(N) (n=D,T) calculations are carried out using a conventional (disk-based) algorithm, where aug(N) stands for the use of the diffuse function augmented aug-cc-pVnZ basis set on the nitrogen atom ... 

Fig. 3. Counterpoise-corrected and uncorrected R and co for the helium dimer, computed with the t-aug-cc-pVnZ sets. The dashed lines represent the estimated CBS limit.

Figure 8 shows the BSSE in Dg for HF, computed at the counterpoise-corrected equilibrium bond length (optimized for each individual basis set). While for Hej the BSSE increases with the addition of diffuse functions to the basis set (see previous section), for HF the BSSE is slightly smaller for the aug-cc-pVnZ sets than for the cc-pVnZ sets. 

As seen above, application of the counterpoise procedure or the addition of diffuse functions may result in Rg(nZ) or coAnZ) curves which are better behaved. As another example. Figure 9 shows the harmonic frequency of HCl, computed with the cc-pVnZ and aug-cc-pVnZ basis sets. As for HF, application of the counterpoise correction improves the convergence behavior of computed with the regular sets, although the convergence behavior of the corrected co, s is far from simple. Addition of the set of diffuse functions to the basis as well as use of the counterpoise correction results in a very smooth dependence of on basis set. 

Examining the results given in these two tables, it is seen that, for this small molecule, very advanced calculations can be carried out. In the tables, all the methods employed have been introduced in the previous sections. For the basis sets, aug-cc-pVnZ stands for augmented correlation consistent polarized valence n zeta, with n = 2-5 referring to double, triple, quadruple, and quintuple, respectively. Clearly, these basis functions are specially designed for... 

Table II. CCSD(T) spectroscopic constants calculated for the state of HglT using the new ECP-based cc-pVitZ-PP (VnZ>PP) and aug-cc-pVnZ (AVr2 PP) basis sets for Hg. The cc-pVitZ and aug-cc-pVnZ basis sets were...

Reference energy (ref) MP4/cc-pVTZ MP4/aug-cc-pVTZ MP2/CBS aug-cc-pVnZ MP2/CBS aug-cc-pVnZ MP2/CBS aug-cc-pVnZ... 

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