Cc-pVnZ

Bauschlicker ANO Available for Sc through Cu (20.vl5/il0r/6/4 ). cc—pVnZ [n = D, T, Q, 5,6) Correlation-consistent basis sets that always include polarization functions. Atoms FI through Ar are available. The 6Z set goes up to Ne only. The various sets describe FI with from i2s p) to [5sAp id2f g) primitives. The Ar atoms is described by from [As pld) to ils6pAd2>f2g h) primitives. One to four diffuse functions are denoted by... 

Dunning has developed a series of correlation-consistent polarized valence n-zeta basis sets (denoted cc-pVnZ ) in which polarization functions are systematically added to all atoms with each increase in n. (Corresponding diffuse sets are also added for each n if the prefix aug- is included.) These sets are optimized for use in correlated calculations and are chosen to insure a smooth and rapid (exponential-like) convergence pattern with increasing n. For example, the keyword label aug-cc-pVDZ denotes a valence double-zeta set with polarization and diffuse functions on all atoms (approximately equivalent to the 6-311++G set), whereas aug-cc-pVQZ is the corresponding quadruple-zeta basis which includes (3d2flg,2pld) polarization sets. 

As the present review was being finalized for publication, we received a preprint by Dunning et al. [12] where new cc-pV(n+d)Z basis sets are proposed for the second-row atoms. These basis sets do have just an added tight d function (hence the acronym) and no tight / functions, but the remaining d functions in the underlying cc-pVnZ basis set are in... 

The denominator shift of 1/2 was chosen as a compromise between the situation for hydrogen and helium (where n = 1 + 1 for the cc-pVnZ basis set) and main-group elements (where n = 1). As is immediately obvious upon series expansion, there is considerable coupling between the denominator shift and the exponent. As a result, the three-point extrapolation generally leads to exponents well in excess of three [34],... 

One plan for the future is the extension to heavier element systems the first step in this direction has been made recently with the development of the SDB-cc-pVnZ valence basis sets [84] (for use with the... 

Figure 4.6 The RMS errors in MP2 correlation energies obtained with the cc-pVnZ basis set (n = Zroax = 2, 3, 4, 5, and 6).

A variety of extrapolation algorithms have been applied to the sequences generated by the correlation-consistent cc-pVnZ basis sets [12, 51-55], Dunning and his colleagues had initially suggested fitting their calculations to an exponentially decaying function [12, 51, 52],... 

Table 4-4 Convergence of the (Zmax + 5) 3 extrapolated cc-pVnZ correlation-consistent basis set MP2 correlation energies (Eh) to the MP2-R12 limit see Eq. (6.2).

The Dunning cc-pVnZ basis sets can be used with our PNO extrapolations to form a potent new combination. We shall consider the SCF energy first, then the MP2 correlation energy, and finally higher-order correlation energy through CCSD(T). 

The PNO extrapolations in Fig. 4.8 and Table 4.6 require localization of the occupied SCF orbitals to ensure size-consistency. In order to preserve this size-consistency for the CBS PNO extrapolations, we have restricted these (Zmax + f)-3 extrapolations to a linear form, Eq. (6.2). The new double extrapolation employs this linear extrapolation of pairs of CBS2/cc-pVnZ calculations and thus is rigorously size-consistent. Note that the nonlinear N-parameter (Zmax + a)-" extrapolations using least-squares fits to more than N cc-pVnZ energies are not size-consistent [53,55],... 

Table 7 Convergence of the scaled PNO extrapolated CBS/cc-pVnZ, correlation-consistent basis set higher-order [i.e. CCSD(T)-MP2] correlation energies (Eh) to the CCSD(T)-R12 limit.

As a first try, we have elected to follow our treatment of the SCF and second-order correlation energies described above, and employ Eq. (6.2) to provide a linear extrapolation of the cc-pVDZ and cc-pVTZ total CBS-CCSD(T) energies obtained with Eq. (2.2), including the interference correction. These total energies reproduce the CCSD(T) limits estimated by Martin [55] via an (lmax + 5)-3 extrapolation of the CCSD(T)/cc-pVDZ, TZ, QZ, 5Z, and 6Z basis sets to within 0.96 kcal/mol RMS error. The agreement with Martin s energies for a small set of chemical reactions is even better (Table 4.8). The use of the cc-pVnZ basis sets for PNO-(Zmax + 5)-3 double extrapolations is indeed promising. 

The orthogonal subspace used in Table I is spanned by the large basis 0=19sl4p8d6f4g3h2i, H=9s6p4d3f2g. The number of basis functions of the large basis that are (nearly) linearly dependent on the cc-pVnZ basis is drastically increased with the cc-pVnZ basis sets. We observe that the externally contracted MP2 calculations converge faster to the MP2 limit. As expected, the energies from the externally contracted MP2 method lie between the standard... 

Figure 3. Basis set errors for the HF energy and CISD correlation energy with the final cc-pVnZ-PP basis sets for the ( , ) 5s 4d, (O, ) 5s4(f, and (A, A) 4

Figure 6. Basis set errors for the HF energy and CISD correlation energy with the final cc-pVnZ-PP basis sets for the ( , ) and (O, ) P states of...

Figure 7. All-electron correlation energies from non-relativistic (NR) and DKrelativistic CISD calculations on the Hg atom using cc-pVnZ-NR and cc-pVnZDK basis sets, respectively.

Table I. CCSD(T) spectroscopic constants calculated for the 11 state of YC using the new ECP-based cc-pVnZ-PP (V/tZ-PP) and all-electron cc- pVQZ (-NR and -DK) basis sets for Y and cc-pV/fZ for C...

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 ... 

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