Small Gold-Thiolate Clusters Au3(SMe)3: Benchmarking of Density Functionals and Bonding Analysis

We present a benchmark study on popular density functionals for their efficiency and accuracy in the geometry and relative stability of gold-thiolate nanoclusters taking Au3(SMe)3 isomers. We have used normalized mean absolute error (NMAE) analysis as a parameter to compare the results with the reference methods - DLPNO-CCSD(T) and RI-SCS-MP2. We have also compared the performance on the thiolate interaction energy of the stable geometries using the results from our benchmark study. One of the promising functional is PBE that shows robust performance for geometry optimization. On the other hand, M06-2X stands out as the proper choice for the relative energies of the clusters. With the selected methods, we have analyzed the gold-sulfur interaction in Au3(SMe)3 and a comparison is made with AuSMe. The bonding analysis has revealed a partial covalency between gold and sulfur atoms in general. On going from AuSMe to Au3(SMe)3, a substantial flow of charge from gold atoms to thiolate ligands as a result of the increase in gold s-d hybridization. As the s-d mixing in Au increases, the main character of Au-S interaction shifts from covalent to ionic. Hence, a covalent-charge-transfer interaction dominates in gold-sulfur bonding and gives rise to a charge-shift bonding.

Density functionals with asymptotic-potential corrections are required for the simulation of spectroscopic properties of materials

Five effects of correction of the asymptotic potential error in density functionals are identified that significantly improve calculated properties of molecular excited states involving charge-transfer character. Newly developed materials-science computational...

Benchmarking Density Functionals, Basis Sets, and Solvent Models in Predicting Thermodynamic Hydricities of Organic Hydrides

Many renewable energy technologies, such as hydrogen gas synthesis and carbon dioxide reduction, rely on chemical reactions involving hydride anions. When selecting molecules to be used in such applications, an important quantity to consider is the thermodynamic hydricity, which is the free energy required for a species to donate a hydride anion. Theoretical calculations of thermodynamic hydricity depend on several parameters, mainly the density functional, basis set, and solvent model. In order to assess the effects of the above three parameters, we carry out hydricity calculations for a set of molecules with known experimental hydricity values, generate linear �fits, and compare the R-squared, root-mean-squared error, and Akaike Information Criterion across different combinations of density functionals, basis sets, and solvent models. Based on these results we are able to quantify the accuracy of theoretical predictions of hydricity and recommend the parameters with the best compromise between accuracy and computational cost.

A Density Functional Theory Investigation of Intramolecular Dispersion Forces in Buckyball-Buckybowl Complexes

<p>The electron-rich, concave face of corannulene makes it an ideal candidate to host electron-deficient fullerenes, such as C60. The host–guest system is dominated by weak van derWaals interactions. Modelling of the C60@corannulene complex was carried out with nine different density functionals: B3LYP, B97-D, BP86, CAM-B3LYP, M06-2X, PW91, t-HCTH, wB97X, and wB97X-D, using the 6-31G(d) basis set. Results indicated that the functionals including an empirical dispersion correction term, B97-D and wB97X-D, gave the most reliable binding energy values when compared with ab initio SCS-MP2 benchmark computations. Additionally, a number of complexes with functionalised corannulene bowls were modelled at the wB97X-D/6-31G(d) level, with NMR calculations performed at the GIAO/wB97X-D/dec-6-31G(d) level. A linear trend was revealed between the number of substituents on corannulene and the strength of binding within complex with C60. Calculated 1H NMR Dd values for methyl groups on methyl substituted corannulene bowls were also linearly dependent on binding energy. Further results are reported here.</p>

A Density Functional Theory Investigation of Intramolecular Dispersion Forces in Buckyball-Buckybowl Complexes

<p>The electron-rich, concave face of corannulene makes it an ideal candidate to host electron-deficient fullerenes, such as C60. The host–guest system is dominated by weak van derWaals interactions. Modelling of the C60@corannulene complex was carried out with nine different density functionals: B3LYP, B97-D, BP86, CAM-B3LYP, M06-2X, PW91, t-HCTH, wB97X, and wB97X-D, using the 6-31G(d) basis set. Results indicated that the functionals including an empirical dispersion correction term, B97-D and wB97X-D, gave the most reliable binding energy values when compared with ab initio SCS-MP2 benchmark computations. Additionally, a number of complexes with functionalised corannulene bowls were modelled at the wB97X-D/6-31G(d) level, with NMR calculations performed at the GIAO/wB97X-D/dec-6-31G(d) level. A linear trend was revealed between the number of substituents on corannulene and the strength of binding within complex with C60. Calculated 1H NMR Dd values for methyl groups on methyl substituted corannulene bowls were also linearly dependent on binding energy. Further results are reported here.</p>