Double-zeta plus polarization valence electrons

HB=BH, diborene, has been studied by ab initio configuration interaction calculations using a double zeta plus polarization basis set. The D h molecule has three low-lying electronic states, 1 Ag, and Zg, just like the O2 molecule, but BgHg has only eight valence electrons. 

Since it would be very expensive to use a STO basis for the four-atom surface calculations, a double-zeta plus polarization (DZP) contracted Gaussian basis is used to determine the behavior of the surface describing the approach of the oxygen atom to the H2O molecule. The results in this basis are compared for H2O to the STO basis and other contracted Gaussian bases in Table 1. In the case of the DZP results, the oxygen Is electrons are kept frozen at the SCF level, so only the valence correlation energy is computed. The... 

Ab initio density functional theory calculations were also carried out on the CH2=XH(A) and CH(A)=XH2 series of molecules. The basis set used was the CEP-TZDP+ described previously26 and is more extensive than the DZP basis set used in the CAS(4,4)-OVB calculations. In TZDP+ the valence electron wave function is expanded in a triple-zeta sp set of functions plus a double set of polarization d-type functions plus a set of diffuse sp-type functions. The B3LYP exchange-correlation functional20 as defined in the Gaussian 94 program set35 was used in all the DFT calculations. 

Reference [111] C3 scheme all electron, LSDA and also GCs (from either Becke 88 [32] or Perdew-Wang (PW86) [33] for the exchange, and Perdew [34] for the correlation). LCGTO double-zeta valence plus polarization (DZVP). 

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