William J. Pietro

Bio: William J. Pietro is an academic researcher from Keele University. The author has contributed to research in topics: Ruthenium & Cyclic voltammetry. The author has an hindex of 29, co-authored 88 publications receiving 10814 citations. Previous affiliations of William J. Pietro include University of California, Irvine & University of York.

Self‐consistent molecular orbital methods. XXIII. A polarization‐type basis set for second‐row elements

Abstract: The 6‐31G* and 6‐31G** basis sets previously introduced for first‐row atoms have been extended through the second‐row of the periodic table. Equilibrium geometries for one‐heavy‐atom hydrides calculated for the two‐basis sets and using Hartree–Fock wave functions are in good agreement both with each other and with the experimental data. HF/6‐31G* structures, obtained for two‐heavy‐atom hydrides and for a variety of hypervalent second‐row molecules, are also in excellent accord with experimental equilibrium geometries. No large deviations between calculated and experimental single bond lengths have been noted, in contrast to previous work on analogous first‐row compounds, where limiting Hartree–Fock distances were in error by up to a tenth of an angstrom. Equilibrium geometries calculated at the HF/6‐31G level are consistently in better agreement with the experimental data than are those previously obtained using the simple split‐valance 3‐21G basis set for both normal‐ and hypervalent compounds. Normal‐mode vibrational frequencies derived from 6‐31G* level calculations are consistently larger than the corresponding experimental values, typically by 10%–15%; they are of much more uniform quality than those obtained from the 3‐21G basis set. Hydrogenation energies calculated for normal‐ and hypervalent compounds are in moderate accord with experimental data, although in some instances large errors appear. Calculated energies relating to the stabilities of single and multiple bonds are in much better accord with the experimental energy differences.

Self-consistent molecular orbital methods. 24. Supplemented small split-valence basis sets for second-row elements

Abstract: The recently introduced 3-21G split-valence basis sets for second-row elements have been supplemented with functionsof d-type symmetry. The resulting basis sets, termed 3-21G(*), are for use in conjuction with unsupplemented 3-21G representationsfor first-row elements. Equilibrium structures calculated by using 3-21G(*) are generally in good accord with available experimentaldata and are markedly improved over the corresponding 3-2 1 G level geometries, especially for hypervalent compounds andfor molecules incorporating bonds between two second-row elements. 3-21G(*) level normal-mode vibration frequencies,hydrogenation energies, and electric dipole moments are also generally but not always in better agreement with their respectiveexperimental quantities than are those obtained by using the unsupplemented 3-21G basis set. Overall, the 3-21G(*) basisset yields molecular properties that are uniformly close to those obtained with the much larger 6-31G* representation. The3-21G(*) basis set is still relatively compact and as such is generally applicable to molecules of moderate size.

Electrochemical Parametrization in Sandwich Complexes of the First Row Transition Metals

Abstract: Applying the ligand electrochemical parameter approach to sandwich complexes and standardizing to the Fe(III)/Fe(II) couple, we obtained E(L)(L) values for over 200 pi-ligands Linear correlations exist between formal potential (E degrees ) and the summation operatorE(L)(L) for each metal couple In this fashion, we report correlation data for many first row transition metal couples The correlations between the E(L)(L) of the substituted pi-ligand and the Hammett substituent constants (sigma(p)) are also explored

Efficient diffuse function‐augmented basis sets for anion calculations. III. The 3‐21+G basis set for first‐row elements, Li–F

Abstract: The relatively small diffuse function-augmented basis set, 3-21+G, is shown to describe anion geometries and proton affinities adequately. The diffuse sp orbital exponents are recommended for general use to augment larger basis sets.

Charge transport in organic semiconductors.

Abstract: 2.2. Materials 929 2.3. Factors Influencing Charge Mobility 931 2.3.1. Molecular Packing 931 2.3.2. Disorder 932 2.3.3. Temperature 933 2.3.4. Electric Field 934 2.3.5. Impurities 934 2.3.6. Pressure 934 2.3.7. Charge-Carrier Density 934 2.3.8. Size/molecular Weight 935 3. The Charge-Transport Parameters 935 3.1. Electronic Coupling 936 3.1.1. The Energy-Splitting-in-Dimer Method 936 3.1.2. The Orthogonality Issue 937 3.1.3. Impact of the Site Energy 937 3.1.4. Electronic Coupling in Oligoacene Derivatives 938

Gaussian-3 (G3) theory for molecules containing first and second-row atoms

Abstract: Gaussian-3 theory (G3 theory) for the calculation of molecular energies of compounds containing first (Li–F) and second row (Na–Cl) atoms is presented. This new theoretical procedure, which is based on ab initio molecular-orbital theory, modifies G2 theory [J. Chem. Phys. 94, 7221 (1991)] in several ways including a new sequence of single point energy calculations using different basis sets, a new formulation of the higher level correction, a spin–orbit correction for atoms, and a correction for core correlation. G3 theory is assessed using 299 energies from the G2/97 test set including enthalpies of formation, ionization potentials, electron affinities, and proton affinities. This new procedure corrects many of the deficiencies of G2 theory. There is a large improvement for nonhydrogen systems such as SiF4 and CF4, substituted hydrocarbons, and unsaturated cyclic species. Core-related correlation is found to be a significant factor, especially for species with unsaturated rings. The average absolute devi...