Single d-metal atoms on the MgO OOl surface

Our group systematically studied single transition metal atoms M deposited on surfaces of ionic metal-oxide supports [252-256]. In some of these studies [252,254], relativistic contributions to the strength of M-0 bonds were thoroughly discussed and found to be rather significant for 4d-metal atoms. 

Another pertinent question is related to the accuracy of the common approximation to describe relativistic effects at the pseudopotential level. Our AE scalar relativistic DKH scheme allows to evaluate the precision of the latter scheme. A relativistic pseudopotential [196] was utilized to treat the heavy element Pd in the Pd-0 complexes employing extended EPE-embedded cluster models of the quality comparable to that for the AE cluster model. This resulted in the adsorption energy value 123 kJ/mol and the Pd-0 bond length 213 pm. For the Pd-0 complexes under scrutiny the deviations from the corresponding scalar relativistic values, by 3 kJ/mol and 2 pm respectively, are rather small. Clearly, relativistic pseudopotentials for heavier atoms have to be constructed with due care [8]. The AE scalar relativistic DKH approach certainly provides an attractive alternative. 

Our comparative scalar relativistic DKH DF BP study of Pds and Pt3 particles, free and deposited on the Al-terminated surface a-Al203(0001), provides another example of notably enhanced relativistic effects when going from 4d to 5d metal moieties [260]. This increase resulted in stronger and shorter bonds formed by 5d metals compared to 4d metals. 

The surface a-Al203(0001) is well suited for building interfaces with hexagonal metal surfaces, where each surface anion interacts with one metal atom. 

With the help of scalar relativistic DKH BP DF calculations, we examined the two structural models of Re(CO)3/MgO complexes at dehydroxylated and hydroxylated MgO surfaces (Fig. 4.8) Re(CO)3 and Re(CO)3 adsorbed on neutral and positively charged Vs centers (Mg defects) [264]. Our aim was (i) to justify the possibility that Re(CO)3/MgO complexes are formed, (ii) to determine their stmctural and spectroscopic parameters, and (iii) to investigate whether the Re-Osurf bonds are similar in strength and nature to common coordination bonds. That work [264] was the first high-level computational study to assess quantitatively stmcture and bonding parameters of an oxide-supported organometallic species. 

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