posted on 2021-08-24, 19:04authored byMartin Blaško, Lukáš
F. Pašteka, Miroslav Urban
Density functional theory (DFT) functionals
for calculations of
binding energies (BEs) of the polyethylene (PE) chains cross-linked
by selected metal atoms (M) are benchmarked against DLPNO–CCSD(T)
and DLPNO–CCSD(T1) data. PEX-M-PEX complexes as compared with
plain parallel PEX···PEX chains with X = 3–9
carbon atoms are model species characterized by a cooperative effect
of covalent C-M-C bonds and interchain dispersion interactions. The
accuracy of DLPNO–CC methods was assessed by a comparison of
BEs with the canonical CCSD(T) results for small PE3-M-PE3 complexes.
Functionals for PEX···PEX and closed-shell PEX-M-PEX
complexes (M = Be, Mg, Zn) were benchmarked against DLPNO–CCSD(T)
BEs; open-shell complexes (M = Li, Ag, Au) were benchmarked against
the DLPNO–CCSD(T1) method with iterative triples. Three dispersion
corrections were combined with 25 DFT functionals for calculations
of BEs with respect to PEX-M and PEX fragments employing def2-TZVPP
and def2-QZVPP basis sets. Accuracy to within 5% for the closed-shell
PEX-M-PEX complexes was achieved with five functionals. Less accurate
are functionals for the open-shell PEX-M-PEX complexes; only two functionals
deviate by less than 15% from DLPNO–CCSD(T1). Particularly
problematic were PEX-Li-PEX complexes. A reasonable overall performance
across all complexes in terms of the mean absolute percentage error
is found for the range-separated hybrid functionals ωB97X-D3
and CAM-B3LYP/D3(BJ)-ABC.