Lanthanide bisphthalocyanine single-molecule magnets: A DFT survey of their geometries and electronic properties from lanthanum to lutetium

Adsorption of lanthanide double-decker phthalocyanines on single-walled carbon nanotubes: structural changes and electronic properties as studied by density functional theory

“…It was impossible to complete the geometry optimization of LnPc 2 +SWCNTs hybrids without the use of thermal smearing, but the value of 10 -4 Ha applied here is very low (equivalent temperature of 31.6 K). At the same time, the structure optimization for LaPc 2 , GdPc 2 and LuPc 2 was afforded also with Fermi occupancy [ 29 ].

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“…In the case of isolated LnPc 2 species, each parameter was compared with the one found in experimentally derived structure XRD from [ 46 , 47 ] (details of such comparisons were described in Ref. [ 29 ]). Also, the formation energies, HOMO, LUMO and HOMO-LUMO gap energies ( E gap ), the charge and spin of central metal atom (Table 2 ), as well as the spin density distribution, were analyzed.…”

“…Moreover, there are already theoretical studies involving specifically MPc 2 complexes that employed this functional [ 9 , 40 – 43 ]. As in a recent study by our group on the optimization of geometry of lanthanide bisphthalocyanines [ 29 ], in all calculations, we employed the DFT semi-core pseudopotentials (DSPP; specially designed to use within DMol 3 module), which implement relativistic effects and spin-orbit coupling, and the double numerical basis set DN, without polarization functions included (equivalent of 6-31G). A global orbital cutoff was set to 4.3 Å (defined by the presence of Ln atoms), and the convergence criteria were as follows: energy gradient, 10 -5 Ha; maximum force, 0.02 Ha/Å; maximum displacement 0.05 Å; SCF tolerance, 10 -4 ; and maximum step size 0.1 Å.…”

“…A global orbital cutoff was set to 4.3 Å (defined by the presence of Ln atoms), and the convergence criteria were as follows: energy gradient, 10 -5 Ha; maximum force, 0.02 Ha/Å; maximum displacement 0.05 Å; SCF tolerance, 10 -4 ; and maximum step size 0.1 Å. As an auxiliary tool to facilitate SCF convergence [ 29 ], thermal smearing was used with a target value of 10 -4 Ha (equivalent temperature of 31.6 K).…”

“…In order to proceed with DFT studies of non-covalent hybrids of LnPc 2 complexes with carbon nanomaterials, it is crucial to obtain the optimized bisphthalocyanine structures, which represent as closely as possible to the ones obtained experimentally by X-ray diffraction (XDR). We focused on this aspect in our previous report [ 29 ]. As opposed to what could be logically expected, the larger DND and DNP basis sets (having polarization functions) were found not to be the best choice for the above purpose, due to (often) unresolvable SCF problems and distorted LnPc 2 geometries (for example, an eclipsed conformation instead of the typical staggered one).…”