Dissociation energy, relativistic effects

Comparing the last two entries in Figure 4.7, the all-electron Douglas-Kroll coupled cluster result for A te is in perfect agreement with the RPPA [156, 157]. Figure 4.8 shows the relativistic effects in dissociation energies. Here, relativistic effects are very sensitive to the level of electron correlation and basis sets used. RPPA... 

CCSD(T) calculations predict a relativistic increase in the dissociation energy of 78kJmol [155]. In comparison, electron correlation increases the dissociation energy by 134kJ mol . Spin-orbit effects increase the dissociation energy further by about 3kJmol [158]. Thus we predict a ArDe value of about SOkJmol. A comparison of calculated force constants reveals a similar picture, see Ref. [131]. 

Figure 4.8 Relativistic increase ApDe in dissociation energy for Au2 calculated in the years from 1989 to 2001 using a variety of different quantum chemical methods. Electron correlation effects AcDg = De(corr.)—De(HF) at the relativistic level are shown on the right hand side of each bar if available. For details see Figure 4.7.

In this section we have concentrated on calculations for H-T only, which have particular relevance to the fine and hyperfine constants determined from Jefferts experiments. Many other papers deal with calculations of the vibration-rotation level energies, for which there is much less experimental data. There are also many papers dealing with the heteronuclear molecule, HD+, which is really a special case because the Bom Oppenheimer approximation collapses, particularly for the highest vibrational levels of the ground electronic state. Even the homonuclear species H and D exhibit some fascinating and unusual effects in their near-dissociation vibration rotation levels. Finally we note that in order to match the accuracy of the experimental measurements for all the hydrogen molecular ion isotopomers, it is necessary to include radiative and relativistic effects. 

Our results therefore clearly demonstrate that there are marked qualitative as well as quantitative differences between the predictions of the NRL and DF SCF calculations for the nature of bonding, total energies, orbital energies, dissociation energies etc., for the diatomics involving actinides due to very significant relativistic effects in such systems. 

Burned that the total atomic relativistic energy is almost independent of the atomic electronic state and the chemical environment in molecules, which implies cancellation of relativistic effects in chemical processes. According to Kolas the correction of the total energy of Hit for relativistic effects amounts to -1.60 cm whereas with the dissociation energy it is only 0,14 cm. Data for H2 are presented in Table 1,3, This table also gives us evidence on the validity of... 

One of the advantages of the relativistic ECP methods is their ability to include spin-orbit effects simultaneously to correlation effects at a reasonable cost. Recently Wiillen [121] the ZORA method to coinage metal diatomics and other others H, F, Cl diatomics. These results for the gold atom are shown in Table 2 where we add other DFT calculations. The agreement of the DFT methods with the experimental values is excellent. The dissociation energy of AuH has also been calculated extensively using several methods. Results are shown in Table 3. 

Table 10 Calculated Bond Lengths r (A) and Bond Dissociation Energies De (kcal/mol) of W-PR3 Bonds of Octahedral W(CO)5PR3 Complexes Using Different Approximations for Relativistic Effects... 

As molecular applications of the extended DK approach, we have calculated the spectroscopic constants for At2 equilibrium bond lengths (RJ, harmonic frequencies (rotational constants (B ), and dissociation energies (Dg). A strong spin-orbit effect is expected for these properties because the outer p orbital participates in their molecular bonds. Electron correlation effects were treated by the hybrid DFT approach with the B3LYP functional. Since several approximations to both the one-electron and two-electron parts of the DK Hamiltonian are available, we dehne that the DKnl -f DKn2 Hamiltonian ( 1, 2= 1-3) denotes the DK Hamiltonian with DKnl and DKn2 transformations for the one-electron and two-electron parts, respectively. The DKwl -I- DKl Hamiltonian is equivalent to the no-pair DKwl Hamiltonian. For the two-electron part the electron-electron Coulomb operator in the non-relativistic form can also be adopted. The DKwl Hamiltonian with the non-relativistic Coulomb operator is denoted by the DKwl - - NR Hamiltonian. 

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