Gaussian-2 theory: Use of higher level correlation methods, quadratic configuration interaction geometries, and second-order Mo\ller–Plesset zero-point energies

Curtiss, Larry A.; Raghavachari, Krishnan; Pople, John A.
September 1995
Journal of Chemical Physics;9/8/1995, Vol. 103 Issue 10, p4192
Academic Journal
The performance of Gaussian-2 theory is investigated when higher level theoretical methods are included for correlation effects, geometries, and zero-point energies. A higher level of correlation treatment is examined using Brueckner doubles [BD(T)] and coupled cluster [CCSD(T)] methods rather than quadratic configuration interaction [QCISD(T)]. The use of geometries optimized at the QCISD level rather than the second-order Mo\ller–Plesset level (MP2) and the use of scaled MP2 zero-point energies rather than scaled Hartree–Fock (HF) zero-point energies have also been examined. The set of 125 energies used for validation of G2 theory [J. Chem. Phys. 94, 7221 (1991)] is used to test out these variations of G2 theory. Inclusion of higher levels of correlation treatment has little effect except in the cases of multiply-bonded systems. In these cases better agreement is obtained in some cases and poorer agreement in others so that there is no improvement in overall performance. The use of QCISD geometries yields significantly better agreement with experiment for several cases including the ionization potentials of CS and O2, electron affinity of CN, and dissociation energies of N2, O2, CN, and SO2. This leads to a slightly better agreement with experiment overall. The MP2 zero-point energies gives no overall improvement. These methods may be useful for specific systems. © 1995 American Institute of Physics.


Related Articles

  • Delayed ionization following photoexcitation of small clusters of refractory elements: Nanofilaments. Amrein, Andreas; Simpson, Richard; Hackett, Peter // Journal of Chemical Physics;3/15/1991, Vol. 94 Issue 6, p4663 

    Photoionization of small clusters of the refractory elements niobium, tantalum, and tungsten at 308 nm is interpreted in terms of a sequential two-photon excitation mechanism in which a rapid coupling between electronic and vibrational degrees of freedom is proposed. Ionization is slow and may...

  • Is coupled cluster singles and doubles (CCSD) more computationally intensive than quadratic configuration interaction (QCISD)? Scuseria, Gustavo E.; Schaefer, Henry F. // Journal of Chemical Physics;4/1/1989, Vol. 90 Issue 7, p3700 

    It is shown that the recently proposed QCI method including all single and double substitutions has essentially the same computational requirements as the more complete CCSD approach. If properly formulated, the CCSD equations contain at most quadratic terms in the excitation amplitudes.

  • Ionization and fragmentation of clusters evaporated from the surface of a metal by accelerated ions. Voıtsekhovskiı, I. A.; Medvedeva, M. V.; Ferleger, V. Kh. // Technical Physics;Dec97, Vol. 42 Issue 12, p1371 

    A mechanism is proposed for the ionization of clusters evaporated from the surface of a metal subjected to fast-ion bombardment. According to this mechanism, part of the internal energy of the cluster nuclei is transferred to its electronic subsystem, with subsequent ionization. Within the...

  • Dynamics of molecules and clusters in intense laser-light fields. Yamanouchi, Kaoru // AIP Conference Proceedings;2002, Vol. 611 Issue 1, p3 

    The investigation of the dynamical behavior of molecules in intense laser fields has afforded us invaluable opportunities to understand fundamentals of the interaction between molecules and light fields as well as to manipulate molecules using characteristics of laser light fields. In the...

  • Comment on ‘‘The weakest bond: Experimental observation of helium dimer’’ [J. Chem. Phys. 98, 3564 (1993)]. Meyer, Eric S.; Mester, John C.; Silvera, Isaac F. // Journal of Chemical Physics;3/1/1994, Vol. 100 Issue 5, p4021 

    Recently, Luo et al. reported indirect evidence for the formation of dimers in a supersonic expansion of helium. They interpreted their data as confirmation of the existence of a bound state of 4He–4He with a binding energy of order 1 mK. We show that their data are actually consistent...

  • Multiphoton ionization studies of clusters of immiscible liquids. II. C6H6–(H2O)n, n=3–8 and (C6H6)2–(H2O)1,2. Garrett, Aaron W.; Zwier, Timothy S. // Journal of Chemical Physics;3/1/1992, Vol. 96 Issue 5, p3402 

    Resonant two-photon ionization (R2PI) time-of-flight mass spectroscopy is used to record S0–S1 spectra of the neutral complexes C6H6–(H2O)n with n=3–8 and (C6H6)2–(H2O)1,2. Due to limitations imposed by the size of these clusters, a number of vibronic level arguments...

  • Ionization potentials of cobalt–sodium bimetallic clusters (ConNam). Hoshino, Kuniyoshi; Naganuma, Takashi; Yamada, Yoshiyuki; Watanabe, Katsura; Nakajima, Atsushi; Kaya, Koji // Journal of Chemical Physics;9/1/1992, Vol. 97 Issue 5, p3803 

    Cobalt–sodium bimetallic clusters (ConNam, n=3–48) were produced by a two independent laser-vaporization method. Ionization potentials of the ConNam clusters were measured up to m=3 using a tunable ultraviolet laser combined with a time-of-flight (TOF) mass spectrometer. In...

  • Structure and stability of Mg+n and Mg++n clusters (n≤7). Durand, G. // Journal of Chemical Physics;11/15/1989, Vol. 91 Issue 10, p6225 

    We present a nonempirical model Hamiltonian of the valence bond type for singly and doubly charged clusters of atoms which have a s2(1S) ground state configuration. This model includes delocalization, instantaneous polarization energies, interaction between induced dipoles, and Coulombic...

  • Short-time charge motion in He[sup +][sub n] clusters. Jeonghee Seong; Janda, Kenneth C. // Journal of Chemical Physics;12/22/1998, Vol. 109 Issue 24, p10873 

    Investigates the ionization of helium[sub n][sup +] clusters. Application of the time-dependent wave packets for the electronic states; Use of the diatomics-in-molecules potential for eigenvalue calculations of positively charged clusters; Characterization of delocalization distance and direction.


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics