Rick A. Kendall

Bio: Rick A. Kendall is an academic researcher from Environmental Molecular Sciences Laboratory. The author has contributed to research in topics: Ab initio & Basis set. The author has an hindex of 19, co-authored 31 publications receiving 13498 citations. Previous affiliations of Rick A. Kendall include Argonne National Laboratory & Pacific Northwest National Laboratory.

Electron affinities of the first-row atoms revisited. Systematic basis sets and wave functions

Abstract: The calculation of accurate electron affinities (EAs) of atomic or molecular species is one of the most challenging tasks in quantum chemistry. We describe a reliable procedure for calculating the electron affinity of an atom and present results for hydrogen, boron, carbon, oxygen, and fluorine (hydrogen is included for completeness). This procedure involves the use of the recently proposed correlation‐consistent basis sets augmented with functions to describe the more diffuse character of the atomic anion coupled with a straightforward, uniform expansion of the reference space for multireference singles and doubles configuration‐interaction (MRSD‐CI) calculations. Comparison with previous results and with corresponding full CI calculations are given. The most accurate EAs obtained from the MRSD‐CI calculations are (with experimental values in parentheses) hydrogen 0.740 eV (0.754), boron 0.258 (0.277), carbon 1.245 (1.263), oxygen 1.384 (1.461), and fluorine 3.337 (3.401). The EAs obtained from the MR‐SD...

The impact of the resolution of the identity approximate integral method on modern ab initio algorithm development

Abstract: The computation of the two-electron four-center integrals over gaussian basis functions is a significant component of the overall work of many ab initio methods used today. Improvements in the computational efficiency of the base algorithms have provided significant impact. Somewhat overlooked are methods that provide approximations to these integrals and their implementation in application software. A partial review of approximate integral techniques focused on the resolution of the identity (RI) four-center, two-electron integral approximation is given. The past and current uses of the RI algorithms are presented along with possibilities for further exploitation of the technology.

Benchmark calculations with correlated molecular wave functions. II. Configuration interaction calculations on first row diatomic hydrides

Abstract: Potential energy functions have been calculated for the electronic ground states of the first row diatomic hydrides BH, CH, NH, OH, and HF using single‐ (HF+1+2) and multi‐ (GVB+1+2 and CAS+1+2) reference internally contracted single and double excitation configuration interaction (CI) wave functions. The convergence of the derived spectroscopic constants and dissociation energies with respect to systematic increases in the size of the one‐particle basis set has been investigated for each method using the correlation consistent basis sets of Dunning and co‐workers. The effect of augmenting the basis sets with extra diffuse functions has also been addressed. Using sets of double (cc‐pVDZ) through quintuple (cc‐pV5Z) zeta quality, the complete basis set (CBS) limits for Ee, De, re, and ωe have been estimated for each theoretical method by taking advantage of the regular convergence behavior. The estimated CBS limits are compared to the available experimental results, and the intrinsic errors associated with each theoretical method are discussed. The potential energy functions obtained from GVB+1+2 and CAS+1+2 calculations are observed to yield very comparable spectroscopic constants, with errors in De ranging from 0.4 kcal/mol for BH to 2.9 kcal/mol for HF. The contraction errors associated with the internally contracted multireference CI have also been calculated for each species; while found to increase from BH to HF, they are, in general, small for all calculated spectroscopic constants. For the cc‐pVDZ basis sets, spectroscopic constants have also been determined from full CI calculations.

Benchmark calculations with correlated molecular wave functions. iii: configuration interaction calculations on first row homonuclear diatomics

Abstract: Using correlation consistent basis sets from double through quintuple zeta quality, potential energy functions have been calculated for the electronic ground states of the first row homonuclear diatomic molecules B2, C2, N2, O2, and F2 using single and double excitation configuration interaction (HF+1+2, GVB+1+2, and CAS+1+2) wave functions. Spectroscopic constants have been calculated for each species and compared to experiment. The dependence of the calculated spectroscopic constants on systematic extensions of the one‐particle basis set are, in general, found to be very regular. By fitting the directly calculated values with a simple exponential function, accurate estimates of the complete basis set (CBS) limit for Ee, De, and re have been obtained for each level of theory. The estimated CBS limits are compared to the available experimental results, and the intrinsic errors associated with each theoretical method are discussed. In addition, the accuracy of the internally contracted CAS+1+2 method is compared to conventional uncontracted calculations using large basis sets. For B2, a full CI calculation have been carried out for De with the correlation consistent double zeta basis set and is compared to the CAS+1+2 method using both a supermolecule and separated atom approach for the dissociated limit.

An extended basis set ab initio study of Li+(H2O)n, n=1–6

Abstract: The structures, binding energies, and enthalpies of small molecular clusters incorporating a single lithium cation and up through six waters have been determined with extended Gaussian basis sets using Hartree–Fock and post‐Hartree–Fock methods. The resulting properties are analyzed with respect to both basis set completeness and degree of correlation recovery, including core–core and core–valence effects. Although the lithium–water interaction is largely electrostatic in nature, small basis sets, lacking in polarization and near‐valence diffuse functions, drastically overestimate the strength of the bond (by 20 kcal/mol or more) and underestimate the Li+...O distance by up to 0.1 A. Their poor performance is attributable to inherent errors in describing the electric moments and polarizability of water and to large basis set superposition errors. Thus, the accuracy with which the fundamental lithium–water interaction could be modeled was primarily dependent on the quality of the Gaussian basis set and not upon the level of correlation recovery. Basis set enlargement and correlation effects both tend to reduce the strength of the Li+(H2O) bond, but produce corrections of opposite sign for the Li+...O bond length. Although correlation effects play a minor role in describing the lithium–water interaction, as the size of the cluster increases and the number of waters involved in multiple hydrogen bonds grows, correlation recovery can become significant.

Semiempirical GGA-type density functional constructed with a long-range dispersion correction.

Abstract: A new density functional (DF) of the generalized gradient approximation (GGA) type for general chemistry applications termed B97-D is proposed. It is based on Becke's power-series ansatz from 1997 and is explicitly parameterized by including damped atom-pairwise dispersion corrections of the form C(6) x R(-6). A general computational scheme for the parameters used in this correction has been established and parameters for elements up to xenon and a scaling factor for the dispersion part for several common density functionals (BLYP, PBE, TPSS, B3LYP) are reported. The new functional is tested in comparison with other GGAs and the B3LYP hybrid functional on standard thermochemical benchmark sets, for 40 noncovalently bound complexes, including large stacked aromatic molecules and group II element clusters, and for the computation of molecular geometries. Further cross-validation tests were performed for organometallic reactions and other difficult problems for standard functionals. In summary, it is found that B97-D belongs to one of the most accurate general purpose GGAs, reaching, for example for the G97/2 set of heat of formations, a mean absolute deviation of only 3.8 kcal mol(-1). The performance for noncovalently bound systems including many pure van der Waals complexes is exceptionally good, reaching on the average CCSD(T) accuracy. The basic strategy in the development to restrict the density functional description to shorter electron correlation lengths scales and to describe situations with medium to large interatomic distances by damped C(6) x R(-6) terms seems to be very successful, as demonstrated for some notoriously difficult reactions. As an example, for the isomerization of larger branched to linear alkanes, B97-D is the only DF available that yields the right sign for the energy difference. From a practical point of view, the new functional seems to be quite robust and it is thus suggested as an efficient and accurate quantum chemical method for large systems where dispersion forces are of general importance.

General atomic and molecular electronic structure system

Abstract: A description of the ab initio quantum chemistry package GAMESS is presented. Chemical systems containing atoms through radon can be treated with wave functions ranging from the simplest closed-shell case up to a general MCSCF case, permitting calculations at the necessary level of sophistication. Emphasis is given to novel features of the program. The parallelization strategy used in the RHF, ROHF, UHF, and GVB sections of the program is described, and detailed speecup results are given. Parallel calculations can be run on ordinary workstations as well as dedicated parallel machines. © John Wiley & Sons, Inc.

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.

Long-range corrected hybrid density functionals with damped atom–atom dispersion corrections

Abstract: We report re-optimization of a recently proposed long-range corrected (LC) hybrid density functional [J.-D. Chai and M. Head-Gordon, J. Chem. Phys., 2008, 128, 084106] to include empirical atom–atom dispersion corrections. The resulting functional, ωB97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent systems, ωB97X-D shows slight improvement over other empirical dispersion-corrected density functionals, while for covalent systems and kinetics it performs noticeably better. Relative to our previous functionals, such as ωB97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions.

Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections

Abstract: Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections Jeng-Da Chai ∗ and Martin Head-Gordon † Department of Chemistry, University of California and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA (Dated: June 14, 2008) We report re-optimization of a recently proposed long-range corrected (LC) hybrid density func- tionals [J.-D. Chai and M. Head-Gordon, J. Chem. Phys. 128, 084106 (2008)] to include empirical atom-atom dispersion corrections. The resulting functional, ωB97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent sys- tems, ωB97X-D shows slight improvement over other empirical dispersion-corrected density func- tionals, while for covalent systems and kinetics, it performs noticeably better. Relative to our previous functionals, such as ωB97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions. I. INTRODUCTION Due to its favorable cost-to-performance ratio, Kohn- Sham density-functional theory (KS-DFT) [1, 2] has be- come the most popular electronic structure theory for large-scale ground-state systems [3–5]. Its extension for treating excited-state systems [6, 7], time-dependent den- sity functional theory (TDDFT), has also been developed to the stage where it is now very widely used. The essential ingredient of KS-DFT, the exchange- correlation energy functional E xc , remains unknown and needs to be approximated. Semi-local gradient-corrected density functionals, though successful in many applica- tions, lead to qualitative failures in some circumstances, where the accurate treatment of non-locality of exchange- correlation hole becomes crucial. These situations occur mostly in the asymptotic regions of molecular systems, such as spurious self-interaction effects upon dissociation [8, 9] and dramatic failures for long-range charge-transfer excitations [10–12]. Widely used hybrid density function- als, like B3LYP [13, 14], do not qualitatively resolve these problems. These self-interaction errors can be qualitatively re- solved using the long-range corrected (LC) hybrid density functionals [15, 16, 18], which employ 100% Hartree-Fock (HF) exchange for long-range electron-electron interac- tions. This is accomplished by a partition of unity, using erf(ωr)/r for long-range (treated by HF exchange) and erfc(ωr)/r for short-range (treated by an exchange func- tional), with the parameter ω controlling the partition- ing. Over the past five years, the LC hybrid scheme has been attracting increasing attention [15] since its compu- tational cost is comparable with standard hybrid func- tionals [13]. However, LC functionals have tended to be inferior to the best hybrids for properties such as ther- mochemistry. ∗ Electronic † Author address: jdchai@berkeley.edu to whom correspondence should be addressed. Electronic address: mhg@cchem.berkeley.edu Recently we have improved the overall accuracy at- tainable with the LC functionals by using a systematic optimization procedure [18]. One important conclusion is that optimizing LC and hybrid functionals with identical numbers of parameters in their GGA exchange and cor- relation terms leads to noticeably better results for all properties using the LC form. The resulting LC func- tional is called ωB97. Further statistically significant improvement results from re-optimizing the entire func- tional with one extra parameter corresponding to an ad- justable fraction of short-range exact exchange, defining the ωB97X functional. Independent test sets covering thermochemistry and non-covalent interactions support these conclusions. However, problems associated with the lack of non-locality of the correlation hole, such as the lack of dispersion interactions (London forces), still remain, as the semi-local correlation functionals cannot capture long-range correlation effects [19, 20]. There have been significant efforts to develop a frame- work that can account for long-range dispersion effects within DFT. Zaremba and Kohn (ZK) [21] derived an exact expression for the second-order dispersion energy in terms of the exact density-density response functions of the two separate systems. To obtain a tractable non- local dispersion functional, Dobson and Dinite (DD) [22] made local density approximations to the ZK response functions. DD’s non-local correlation functional was ob- tained independently [23] by modifying the effective den- sity defined in the earlier work of Rapcewicz and Ashcroft Starting from the formally exact expression of KS- DFT, the adiabatic connection fluctuation-dissipation theorem (ACFDT), for the ground-state exchange- correlation energy, Langreth and co-workers [25] devel- oped a so-called van der Waals density functional (vdW- DF) by making a series of reasonable approximations to yield a computationally tractable scheme. Recently, Becke and Johnson (BJ) developed a series of post-HF correlation models with a novel treatment for dispersion interactions based on the exchange-hole dipole moment [26]. The origin of dispersion claimed in the BJ models was recently questioned by Alonso, and A.