Q-Chem 2.0: a high-performanceab initio electronic structure program package

Kong, Jing; White, Christopher A.; Krylov, Anna I.; Sherrill, C. David; Adamson, Ross D.; Furlani, Thomas R.; Lee, Michael S.; Lee, Aaron M.; Gwaltney, Steven R.; Adams, Terry R.; Ochsenfeld, Christian; Gilbert, Andrew T. B.; Kedziora, Gary S.; Rassolov, Vitaly A.; Maurice, David; Nair, Nikhil U.; Shao, Yihan; Besley, Nicholas A.; Maslen, Paul E.; Dombroski, Jeremy P.; Daschel, Holger; Zhang, Weimin; Korambath, Prakashan; Baker, Jon; Byrd, Edward F. C.; Voorhis, Troy A. Van; Oumi, Manabu; Hirata, So; Hsu, Chao‐Ping; Ishikawa, Naoto; Florián, Jan; Warshel, Arieh; Johnson, Benny G.; Gill, Peter M. W.; Head‐Gordon, Martin; Pople, John A.

doi:10.1002/1096-987x(200012)21:16<1532::aid-jcc10>3.0.co;2-w

Cited by 617 publications

(334 citation statements)

References 99 publications

Supporting

Mentioning

330

Contrasting

Unclassified

Order By: Relevance

“…Halkier et al have studied the convergence of the HF energy using correlation consistent basis sets and report that using the cc-pV5Z basis yields energies within 1 mE h of the HF limit [25]. All HF energies are calculated using the Q-CHEM package [26].…”

Section: Resultsmentioning

confidence: 99%

Benchmark correlation energies for small molecules

O’Neill¹,

Gill

2005

Molecular Physics

View full text Add to dashboard Cite

show abstract

Section: Resultsmentioning

confidence: 99%

Benchmark correlation energies for small molecules

O’Neill¹,

Gill

2005

Molecular Physics

View full text Add to dashboard Cite

show abstract

“…We have modified our standard MP2 program for energies and gradients [41] to implement the SOS-MP2 and SCS-MP2 energy and gradient, within a development version of the Q-Chem program [42]. This was used for all calculations reported in this section.…”

Section: Chemical Testsmentioning

confidence: 99%

Scaled opposite-spin second order Møller–Plesset correlation energy: An economical electronic structure method

Jung

Lochan²,

Dutoi³

et al. 2004

The Journal of Chemical Physics

Self Cite

550

661

View full text Add to dashboard Cite

Abstract.A simplified approach to treating the electron correlation energy is suggested in which only the alpha-beta component of the second order Møller-Plesset energy is evaluated, and then scaled by an empirical factor which is suggested to be 1.3. This scaled opposite spin second order energy (SOS-MP2) yields results for relative energies and derivative properties that are statistically improved over the conventional MP2 method. Furthermore, the SOS-MP2 energy can be evaluated without the 5th order computational steps associated with MP2 theory, even without exploiting any spatial locality. A 4th order algorithm is given for evaluating the opposite spin MP2 energy using auxiliary basis expansions, and a Laplace approach, and timing comparisons are given. * These authors contributed equally to this work. † To whom correspondence should be addressed. E-mail: mhg@cchem.berkeley.edu 2 1.Introduction.The most popular electronic structure method for application to systems with large numbers of electrons is density functional theory (DFT) [1,2]. However DFT methods at present completely neglect the dispersion interactions [3] that give rise to base pair stacking and other long-range correlation effects (for example the TCNE dimer dianion [4]). Novel workarounds are being explored for dispersion interactions of monomers [5][6] or ordered layers and surfaces [7,8], but do not presently apply to molecular systems. More empirical modifications of standard functionals have also been developed to improve non-bonded interactions [9,10]. Also we note that present-day DFT methods are somewhat suspect for reaction barriers. Standard functionals tend to underestimate activation energies [11], largely as a consequence of the self-interaction issue [12].The simplest electronic structure alternative to DFT that can correctly treat dispersion and hydrogen-bonding interactions is second order Møller-Plesset theory (MP2) [13]. MP2 theory is capable of quite accurately treating long-range dispersion interactions [14], as well as the dispersion, polarization and covalency effects associated with hydrogen bonding (for instance in water clusters [15]). However, MP2 has several significant drawbacks: First is relatively high computational cost, even with the best standard algorithms. Second is the need for quite large atomic orbital basis sets in order to obtain good results [16], which can further reduce the upper limit on system size. Third is the fact that poor results can be obtained for open shell systems [17], in contrast to the good behavior for closed shell molecules [18].There has been significant progress in addressing the steep cost increase of MP2calculations with molecular size in recent years. Three main types of developments can be 3 identified. First are methods that reduce the prefactor without changing the underlying scaling, such as "resolution of the identity" methods [19,20] or the pseudo-spectral approach [21], and others [22]. Second are methods that attempt to exploit "underlying locality" in the MP2problem, w...

show abstract

“…The atomic partial charges of the different electronic transitions from the ground state were obtained by a fit of the ab initio electrostatic potential of the transition density, calculated with time-dependent density functional theory, a B3LYP exchange correlation functional and a 6-31G* basis set. The quantum chemical calculations were performed with Jaguar (37) and QChem (38) and the fit of the electrostatic potential of the transition densities [TrEsp method (30)] with CHELP-BOW (39). The Poisson equation (Eq.…”

Section: Computational Proceduresmentioning

confidence: 99%

Theory of solvatochromic shifts in nonpolar solvents reveals a new spectroscopic rule

Renger

Grundkötter²,

Madjet³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

An expression of unexpected simplicity is derived for the shift in optical transition energies of solute molecules in nonpolar solvents. The expression reveals a new spectroscopic rule that says: The higher the excited state of the solute, the larger the solvatochromic red shift. A puzzle formulated >50 years ago by Bayliss is solved. Bayliss, based on arguments from classical physics, assumed that the shift scales with the oscillator strength of the solute transition, but noted strong quantitative deviations from this rule in experiments. As the present expression shows, the shift does not depend on the oscillator strength of the transition, but reflects the change in dispersive solute-solvent interactions between the ground and excited states of the solute, that are determined by the anisotropy of intramolecular electron correlation. The theory is applied to explain the solvatochromic shifts of the two lowest electronic excitations of bacteriochlorophyll a and bacteriopheophytin a.dispersive interactions ͉ extended dipole ͉ oscillator strength sum rule ͉ solvation energy ͉ transition density W hen a dye molecule is moved from the gas phase into a solvent, a solvent-specific alteration of its optical properties results. The change of optical transition energies of the solute is termed solvatochromic shift. The latter results from the difference in solute-solvent interactions of the solute's ground and excited state. In a polar solvent, the major part of the shift is caused by the change of the charge density of the solute that occurs on optical excitation. This effect can be understood in terms of classical physics. The charge density of the solute polarizes the solvent and this polarization acts back on the solute. The interaction energy between this so-called reaction field of the polarization and the charge density is termed solvation energy. It is the difference in solvation energies between the solute's ground and excited states that gives rise to the solvatochromic shift. The solvation energy of the excited state is a nonequilibrium quantity (1), because the slow nuclear part of the solvent polarization cannot follow the optical excitation and therefore initially stays relaxed with respect to the ground-state charge density of the solute (Franck-Condon principle).In a nonpolar solvent, the solvent molecules do not have a permanent dipole moment and mainly their electron clouds are polarized by the charge density of the solute molecule. Besides this so-called inductive interaction, the dispersive solute-solvent interaction becomes important in nonpolar solvents. As recognized by London (2), even a molecule with no permanent dipole moment, because of the quantum mechanical uncertainty principle, will have a fluctuating dipole moment that can polarize its neighbor, giving rise to the van der Waals interaction between two nonpolar molecules in their electronic ground states. The idea of London can be generalized to describe the coupling between an excited solute molecule and the solvent. Before a detailed tre...

show abstract

Q-Chem 2.0: a high-performanceab initio electronic structure program package

Cited by 617 publications

References 99 publications

Benchmark correlation energies for small molecules

Benchmark correlation energies for small molecules

Scaled opposite-spin second order Møller–Plesset correlation energy: An economical electronic structure method

Theory of solvatochromic shifts in nonpolar solvents reveals a new spectroscopic rule

Contact Info

Product

Resources

About