Paul G. Jasien

Bio: Paul G. Jasien is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Ab initio & Ab initio quantum chemistry methods. The author has an hindex of 8, co-authored 10 publications receiving 2330 citations.

Relativistic compact effective potentials and efficient, shared-exponent basis sets for the third-, fourth-, and fifth-row atoms

Abstract: Relativistic compact effective potentials (RCEP), which replace the atomic core electrons in molecular calculations, have been derived from numerical Dirac–Fock atomic wavefunctions using shape-con...

Ab initio study of the hydrogen bonding interactions of formamide with water and methanol

Abstract: Ab initio calculations of hydrogen bond energies for a number of water–formamide and methanol–formamide complexes are reported at both the SCF and correlated levels. Full gradient optimizations of these structures have been performed for basis sets of double zeta and double zeta plus polarization quality. For both water and methanol, the most stable 1:1 complex is found to be a cyclic double hydrogen bonded structure. Basis set effects on the calculated hydrogen bond energies were investigated as was the magnitude of the basis set superposition error. In all cases investigated, the addition of polarization functions to the basis set is found to decrease the calculated binding energy by approximately 2–4 kcal/mol, while correlation is found to increase the binding energy by ≂1 kcal/mol. Calculations on dihydrated formamide indicate a small three‐body contribution to the total binding energy.

Possible precursors in HCN oligomerization

Abstract: Ab initio self-consistent field calculations have been used to characterize the electronic structure and to predict geometrical parameters of H2C2N2 isomers. Only three isomers along with the linear (HCN)2 hydrogen-bonded complex are predicted to be lower in energy than two non-interacting HCN monomers. Large scale correlation calculations led to only small refinements in the relative energetics. The most stable isomer is iminoacetonitrile, a fact which enhances the possibility of its role in HCN oligomerization. However, this isomer has not been spectroscopically characterized in the gas phase and so accurate predictions of equilibrium rotational constants for iminoacetonitrile as well as the other isomers are reported.

Calculated proton affinities for some molecules containing group VIA atoms

Abstract: The proton affinities and structures of a series of small molecules containing group VIA atoms are calculated via ab initio electronic structure techniques. The series under study included CX, OCX, XCX, and H2CX, where X=O, S, Se, and Te. In those cases where multiple protonation sites are available, a definitive assignment of the most stable site is reported. Excellent agreement with the experimentally known proton affinities is found in almost all cases. The results indicate that the general trend which one would expect upon moving down a column of the periodic table is born out, with a particularly large change on going from the first to the second row. Calculations were performed at both the SCF and correlated levels with compact effective potentials used to replace the core electrons. Complete structural optimizations via analytic gradients were performed utilizing basis sets of at least double zeta plus polarization quality.

Toward reliable density functional methods without adjustable parameters: The PBE0 model

Abstract: We present an analysis of the performances of a parameter free density functional model (PBE0) obtained combining the so called PBE generalized gradient functional with a predefined amount of exact exchange. The results obtained for structural, thermodynamic, kinetic and spectroscopic (magnetic, infrared and electronic) properties are satisfactory and not far from those delivered by the most reliable functionals including heavy parameterization. The way in which the functional is derived and the lack of empirical parameters fitted to specific properties make the PBE0 model a widely applicable method for both quantum chemistry and condensed matter physics.

A new local density functional for main-group thermochemistry, transition metal bonding, thermochemical kinetics, and noncovalent interactions.

Abstract: We present a new local density functional, called M06-L, for main-group and transition element thermochemistry, thermochemical kinetics, and noncovalent interactions. The functional is designed to capture the main dependence of the exchange-correlation energy on local spin density, spin density gradient, and spin kinetic energy density, and it is parametrized to satisfy the uniform-electron-gas limit and to have good performance for both main-group chemistry and transition metal chemistry. The M06-L functional and 14 other functionals have been comparatively assessed against 22 energetic databases. Among the tested functionals, which include the popular B3LYP, BLYP, and BP86 functionals as well as our previous M05 functional, the M06-L functional gives the best overall performance for a combination of main-group thermochemistry, thermochemical kinetics, and organometallic, inorganometallic, biological, and noncovalent interactions. It also does very well for predicting geometries and vibrational frequencies. Because of the computational advantages of local functionals, the present functional should be very useful for many applications in chemistry, especially for simulations on moderate-sized and large systems and when long time scales must be addressed. © 2006 American Institute of Physics. DOI: 10.1063/1.2370993

A combined quantum mechanical and molecular mechanical potential for molecular dynamics simulations

Abstract: A combined quantum mechanical (QM) and molecular mechanical (MM) potential has been developed for the study of reactions in condensed phases. For the quantum mechanical calculations semiempirical methods of the MNDO and AM1 type are used, while the molecular mechanics part is treated with the CHARMM force field. Specific prescriptions are given for the interactions between the QM and MM portions of the system; cases in which the QM and MM methodology is applied to parts of the same molecule or to different molecules are considered. The details of the method and a range of test calculations, including comparisons with ab initio and experimental results, are given. It is found that in many cases satisfactory results are obtained. However, there are limitations to this type of approach, some of which arise from the AM1 or MNDO methods themselves and others from the present QM/MM implementation. This suggests that it is important to test the applicability of the method to each particular case prior to its use. Possible areas of improvement in the methodology are discussed.

Correlation consistent valence basis sets for use with the Stuttgart–Dresden–Bonn relativistic effective core potentials: The atoms Ga–Kr and In–Xe

Abstract: We propose large-core correlation-consistent (cc) pseudopotential basis sets for the heavy p-block elements Ga–Kr and In–Xe. The basis sets are of cc-pVTZ and cc-pVQZ quality, and have been optimized for use with the large-core (valence-electrons only) Stuttgart–Dresden–Bonn (SDB) relativistic pseudopotentials. Validation calculations on a variety of third-row and fourth-row diatomics suggest them to be comparable in quality to the all-electron cc-pVTZ and cc-pVQZ basis sets for lighter elements. Especially the SDB-cc-pVQZ basis set in conjunction with a core polarization potential (CPP) yields excellent agreement with experiment for compounds of the later heavy p-block elements. For accurate calculations on Ga (and, to a lesser extent, Ge) compounds, explicit treatment of 13 valence electrons appears to be desirable, while it seems inevitable for In compounds. For Ga and Ge, we propose correlation consistent basis sets extended for (3d) correlation. For accurate calculations on organometallic complexes o...