MIDI basis sets

MAXI—i and MIDI Are higher-accuracy basis sets derived from the MIDI basis set. 

Firstly, inclusion of polarization functions on the C and H atoms of the reactive groups (CH3 and C2H4) reduces considerably the insertion barrier (compare runs 1 and 2 as well as runs 6 and 7 ) and seems to be mandatory. Instead, inclusion of polarization functions on the ancillary H2Si(Cp)2 ligand has a negligible effect on the calculated insertion barrier (compare runs 2 and 3 as well as runs 7 and 8). Extension of the basis set on the reactive groups lowers further the insertion barrier (compare runs 7 and 9). Both the MIDI basis set on Zr, and the SVP basis set on the remaining atoms decrease the insertion barrier (compare runs 3, 5 and 8). Finally, the extension of the active orbitals space to include all the occupied orbitals reduces sensibly the insertion barrier (compare runs 3 and 4). 

The molecular stmctures of molecular iodine complexes with nucleotides adenosine (VI) and guanosine (VII) and LiCl were studied using computational methods. The DFT/B3PW91 method with the 6-31G basis set for the atoms of C, N, O, H, Li, Cl and the midi basis set for I was applied. The considered complexes were fully optimized (Fig. 10.4). 

Figure 3. The differences between the CCSD(T) (a) and CR-CCSD(T) (b) energies and the full Cl energies (in eV) for the collinear BeFH system, as described by the MIDI basis set [121], as functions of the H-F and Be-F internuclear separations, Rh-p and Reb-f, respectively (in bohr). For the original numerical data, see Ref. [37].

MIDI—i Same primitives as the MINI basis sets with two contractions to describe the valence orbitals for greater flexibility. 

In order to investigate the basis set effects on the insertion barrier, single point MP2 calculations on the MP2/MIDI-SVP geometries are reported in Table 5. 

One feature of the Pople basis sets is that they use a so-called segmented contraction. This implies that the primitives used for one basis function are not used for another of the same angular momentum (e.g., no common primitives between the 2s and 3s basis functions for phosphorus). Such a contraction scheme is typical of older basis sets. Other segmented split-valence basis sets include the MIDI and MAXI basis sets of Huzinaga and co-workers, which are named MIDI-1, MIDI-2, etc., MAXI-1, MAXI-2, etc. and vary in the number of primitives used for different kinds of functions. 

In die Pople family of basis sets, the presence of diffuse functions is indicated by a + in die basis set name. Thus, 6-31- -G(d) indicates that heavy atoms have been augmented with an additional one s and one set of p functions having small exponents. A second plus indicates the presence of diffuse s functions on H, e.g., 6-311- -- -G(3df,2pd). For the Pople basis sets, die exponents for the diffuse functions were variationally optimized on the anionic one-heavy-atom hydrides, e.g., BH2 , and are die same for 3-21G, 6-3IG, and 6-3IIG. In the general case, a rough rule of thumb is diat diffuse functions should have an exponent about a factor of four smaller than the smallest valence exponent. Diffuse sp sets have also been defined for use in conjunction widi die MIDI and MIDIY basis sets, generating MIDIX+ and MIDIY-I-, respectively (Lynch and Truhlar 2004) the former basis set appears pardcularly efficient for the computation of accurate electron affinities. 

Modihed JNeglect of Diatomic Overlap fMNDO) 3.10.4 Austin Model 1 (AMI) 86 87 5.4.3 MINI, MIDI and MAXI Basis Sets 5.4.4 Atomic Natural Orbitals Basis Sets 161 161... 

Basis set used here is midi plus p-type orbital for Cr ions and 6-3IG for other atoms Equation (18.11) is used / -factor is 3.4 % [18]... 

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