Cholesky Decomposition-Based Implementation of Relativistic Two-Component Coupled-Cluster Methods for Medium-Sized Molecules

A Cholesky decomposition (CD)-based implementation of relativistic two-component coupled-cluster (CC) and equation-of-motion CC (EOM-CC) methods using an exact two-component Hamiltonian augmented with atomic-mean-field spin–orbit integrals (the X2CAMF scheme) is reported. The present CD-based implementation of X2CAMF-CC and EOM-CC methods employs atomic-orbital-based algorithms to avoid the construction of two-electron integrals and intermediates involving three and four virtual indices. Our CD-based implementation extends the applicability of X2CAMF-CC and EOM-CC methods to medium-sized molecules with the possibility to correlate around 1000 spinors. Benchmark calculations for uranium-containing small molecules were performed to assess the dependence of the CC results on the Cholesky threshold. A Cholesky threshold of 10–4 is shown to be sufficient to maintain chemical accuracy. Example calculations to illustrate the capability of the CD-based relativistic CC methods are reported for the bond-dissociation energy of the uranium hexafluoride molecule, UF6, with up to quadruple-ζ basis sets, and the lowest excitation energy in the solvated uranyl ion [UO22+(H2O)12]

Cholesky Decomposition-Based Implementation of Relativistic Two-Component Coupled-Cluster Methods for Medium-Sized Molecules

A Cholesky decomposition (CD)-based implementation of relativistic two-component coupled-cluster (CC) and equation-of-motion CC (EOM-CC) methods using an exact two-component Hamiltonian augmented with atomic-mean-field spin–orbit integrals (the X2CAMF scheme) is reported. The present CD-based implementation of X2CAMF-CC and EOM-CC methods employs atomic-orbital-based algorithms to avoid the construction of two-electron integrals and intermediates involving three and four virtual indices. Our CD-based implementation extends the applicability of X2CAMF-CC and EOM-CC methods to medium-sized molecules with the possibility to correlate around 1000 spinors. Benchmark calculations for uranium-containing small molecules were performed to assess the dependence of the CC results on the Cholesky threshold. A Cholesky threshold of 10–4 is shown to be sufficient to maintain chemical accuracy. Example calculations to illustrate the capability of the CD-based relativistic CC methods are reported for the bond-dissociation energy of the uranium hexafluoride molecule, UF6, with up to quadruple-ζ basis sets, and the lowest excitation energy in the solvated uranyl ion [UO22+(H2O)12]

Optically Active β‑Methyl-δ-Valerolactone: Biosynthesis and Polymerization

Chemo-enzymatic pathways were developed to prepare optically enriched (+)-β-methyl-δ-valerolactone and (−)-β-methyl-δ-valerolactone. Anhydromevalonolactone, synthesized by the acid-catalyzed dehydration of bioderived mevalonate, was transformed to (+)-β-methyl-δ-valerolactone with 76% ee and 69% conversion using the mutant enoate reductase, YqjM­(C26D, I69T). With the same substrate but a different enoate reductase (OYE2), we obtained the other enantiomer ((−)-β-methyl-δ-valerolactone) with higher selectivity and yield (96% ee and a 92% conversion). The enzyme-docking program LibDock was used to help explain the origin of the divergent enatntioselectivity of the two reductases, and complementary <i>in vitro</i> experiments were used to determine the turnover number and Michaelis constant for each. Finally, the effect of the enantiopurity of the β-methyl-δ-valerolactone monomer on the properties of the corresponding polyester was investigated. Like atactic poly((±)-β-methyl-δ-valerolactone), the isotactic polymer was determined to be amorphous with a low softening temperature (−52 °C)