Hay-Wadt

SBKJC VDZ Available for Li(4.v4/>) through Hg(7.v7/ 5d), this is a relativistic basis set created by Stevens and coworkers to replace all but the outermost electrons. The double-zeta valence contraction is designed to have an accuracy comparable to that of the 3—21G all-electron basis set. Hay-Wadt MB Available for K(5.v5/>) through Au(5.v6/ 5r/), this basis set contains the valence region with the outermost electrons and the previous shell of electrons. Elements beyond Kr are relativistic core potentials. This basis set uses a minimal valence contraction scheme. These sets are also given names starting with LA for Los Alamos, where they were developed. 

Some of the basis sets discussed here are used more often than others. The STO—3G set is the most widely used minimal basis set. The Pople sets, particularly, 3—21G, 6—31G, and 6—311G, with the extra functions described previously are widely used for quantitative results, particularly for organic molecules. The correlation consistent sets have been most widely used in recent years for high-accuracy calculations. The CBS and G2 methods are becoming popular for very-high-accuracy results. The Wachters and Hay sets are popular for transition metals. The core potential sets, particularly Hay-Wadt, LANL2DZ, Dolg, and SBKJC, are used for heavy elements, Rb and heavier. 

Slovenia), using the DFT implementation in the Gaussian03 code. Revision C.02 (8). The orbitals were described by a mixed basis set. A fully uncontracted basis set from LANL2DZ was used for the valence electrons of Re (9), augmented by two / functions Q =1.14 and 0.40) in the full optimization. Re core electrons were treated by the Hay-Wadt relativistic effective core potential (ECP) given by the standard LANL2 parameter set (electron-electron and nucleus-electron). The 6-3IG basis set was used to describe the rest of the system. The B3PW91 density functional was used in all calculations. 

Popular pseudopotentials in modem use include those of Hay and Wadt (sometimes also called the Los Alamos National Laboratory (or LANE) ECPs Hay and Wadt 1985), those of Stevens et al. (1992), and the Stuttgart-Dresden pseudopotentials developed by Dolg and co-workers (2002). The Hay-Wadt ECPs are non-relativistic for the first row of transition metals while most others are not as relativistic effects are usually quite small for this region of the periodic table, the distinction is not particularly important. Lovallo and Klobukowski (2003) have recently provided additional sets of both relativistic and non-relativistic ECPs for these metals. Eor the p block elements. Check et al. (2001) have optimized polarization and diffuse functions to be used in conjunction with the LANE double-t basis set. 

Examination of the geometrical parameters in Table 2 shows that the Ga-N bonds are only slightly longer than Al-N and that the Ga-H bonds have similar distances to the Al-H bonds. The use of an RECP made little difference, except that the MP2/CEP-121G Ga-H distance was consistently —0.03 A shorter than MP2/6-31G and a similar trend of —0.01 shorter Ga-N distances with the RECP. The Al-N and Ga-N bond distances compare favorably with the shortest experimental monoamide values (1.784 and 1.847 A, respectively (17). Pink et al. also used the Hay-Wadt effective core potential (21) to optimize H2GaNH2, getting 1.794 A for the Ga-N distance (17). This is 0.02 A shorter than with the CEP-121G basis. 

Calculations were carried out with the GAUSSIAN 98 program [10]. Geometries of the structures were optimized with the B3LYP functional. Harmonic vibration frequencies were calculated for each structure. LANL2DZ basis set (the Hay-Wadt effective core potential [11] plus double-zeta basis for molybdenum and aluminium atoms, Dunning-Huzinaga valence double-zeta basis set for other elements) was employed. 

Hay and Wadt (1985a, b) have published ECPs which are in form identical to the averaged RECPs of Christiansen, Ermler and co-workers. However, there are differences. First, the Hay-Wadt potentials are derived from the Cowan-GriflSn adaptation of the Breit-Pauli Hamiltonian into a variational computation of the atomic wave-function. From these solutions the ECPs are generated. It should be noted that the spin-orbit coupling is not included in the Hay-Wadt ECPs. Consequently, molecular calculations done using these ECPs would not include spin-orbit coupling. 

For accurate calculations of TM compounds, f-type polarization functions should be added to the basis set. Exponents for f-polarization functions have been optimized by us for the Hay-Wadt ECP. No other sets of f-type functions optimized for use with pseudopotentials are known to us. However, because the valence orbitals of the pseudopotentials mimic the all-electron orbitals, the f-type functions determined for all-electron cases can also be used for pseudopotential calculations. 

Now we discuss calculated bond dissociation energies. The Stoll-Preuss ECPs proved to be clearly superior to the Hay-Wadt ECPs for this project, so... 

Table 13 Calculated and Experimental Metal—Carbon Bond Dissociation Energies Dg (kcal/mol) of Group 11 and 12 Methyl and Phenyl Compounds Using Hay—Wadt Pseudojxrtentials Geometries Optimized at MP2/II (see Table 12)... 

Figure 2 Plot of Cl—Cl distance versus relative total energy of CI2 for all-electron (AE) and ECPs of Hay-Wadt (HW), Kahn-Baybutt-Truhlar (KBT), and Christiansen-Lee-Pitzer (CLP). ...

The Hay-Wadt (HW) and all-electron (AE) model potential and experimental results are taken from References 59 and 60. The SBK results utilize the Stevens potentials augmented with a d polarization function and diffuse sp bases on all atoms to make them comparable in valence basis sets to the other calculations. 

The other known EGP and valence-electron basis sets were generated using the procedure, described for Hay-Wadt ECP generation. Durand-Barthelat large-core semilocal ECP [484] and corresponding valence-electron basis sets are generated for 3d-transition elements and the main-group elements Li to Kr. 

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