Basis sets TZVPP

Fig. 10. Energy spectrum for the lower electronic states of Cr(H20)l+, along the path of the normal mode of vibration, calculated using the CASSCF(4,5) method and the TZVPP basis set.

RI-MP2/TZVPP, extrapolating to the complete basis set and including corrections fromCCSD(T). 

Geometry optimized at R1-MP2/TZVPP, energy from a complete basis set extrapolation with CCSD(T) correction, Ref 115. 

To test the performance of the SVP-SV(P) basis set, the energy of points along a trajectory was recomputed with ADC(2)/TZVPP. The results show only minor differences between the two levels (<3 kcal mol ) in the excited-state energy profile (see Figure S3 of the Supplementary Material). 

A geometry optimization of Tc2(02CCH3)2Cl4 was performed using the Tao, Perdew, Staroverov, and Scuseria hybrid functional (TPSSh) at the triple-zeta valence plus polarization (TZVPP) basis set [53]. The results show that the calculated Tc-Tc, Tc-Cl, and Tc-O bond distances are in good agreement with the experimental values (Table 7.5). The largest deviation is found for the Tc-Tc distance. 

The counterpoise correction typically overestimates the BSSE since the monomer basis set is enhanced not only by empty orbitals of the other fragment, but also by orbitals occupied by electrons of the other monomer molecule which are excluded by the Pauli principle. Thus, if CP-corrected and uncorrected interaction energies are plotted as function of basis set size, they approach from above and below, respectively, the true interaction energy at the complete basis set (CBS) limit. CP corrections are mandatory for all double-zeta calculations and with MP2 or CCSD(T) also for triple-zeta basis treatments. In triple-zeta basis set (e.g., cc-pVTZ or TZVPP) DPT calculations, the BSSE is typically less than 5-10% of the interaction energy which makes the laborious CP correction unnecessary. If sets of valence quadruple-zeta are used, it seems as if the error of the CP procedure is often similar to the (uncorrected) BSSE, but this is system-dependent and more definite conclusions about this issue requires further work. 

TZVP, TZVPP, QZVP, and QZVPP basis sets (from left to right, characterized by their numb j of spherical harmonic basis functions) for the molecules of the test set at levels DFT(BP86), upper part and MP2, lower part... 

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