Correlated ab Initio Electronic Structure Calculations for Large Molecules

“…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 MP2…”

mentioning

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

542

661

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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...

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“…RCE value obtained using basis set 6-311G(3d1f , 3p) and corrected by zero point energy (∆ ZPE = 0.07 [8]) is equal to −0.40 kcal/mol and is within the scope of experimental data.…”

Section: -Fluoropropanementioning

confidence: 54%

“…Theoretical estimates −0.01 and −0.16 kcal/mol obtained using HF and LMP2 calculations with extended cc-pVTZ(−f ) basis set [8] respectively have the correct sign, but demonstrate large discrepancy with experimental data in value. Recent calculations of energy difference E G − E A performed in [9] at HF, MP2, and B3LYP levels using DZ and TZ basis sets show the energy of gauche form being lower than anti (Table 1).…”

Section: -Fluoropropanementioning

confidence: 82%

“…Theoretical evaluations obtained using HF/6-31G(d) ( Table 2) do not exhibit the presence of gauche effect, whereas HF and LMP2 with extended basis set (cc-pVTZ (−f )) reveal the preference of gauche form (−0.13 and −0.55 kcal/mol respectively [8]). The calculations performed in [12] using MP2, G2/MP2, and B3LYP methods as well as TZ basis set with polarization and diffuse functions included demonstrate good agreement with experimental data, the E G − E A value being approximately −0.8 kcal/mol.…”

Section: 2-difluoroethanementioning

confidence: 99%

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Additivity of conformational energy: Quantum mechanical investigation of fluoro- and bromoalkanes

Jankauskas¹

2007

Lithuanian J. Phys.

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The possibility to use additivity rule [1] for estimation of relative conformational energies of fluoro-and bromo-substituted alkanes is studied. The ability of quantum mechanical methods (HF and MP2) to estimate the additivity increments EThe obtained results have been compared with available experimental data. It is shown that increments are sensitive to the method and basis set used. The arrangement of relative conformational energies for various conformers in the series of polysubstituted fluoro-and bromoalkanes obtained using additivity rule agrees both with experimental findings and quantum mechanical calculations. The results lead to the conclusion that it is possible to work out the quantum mechanically based additivity schemes for investigated compounds.

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Correlated ab Initio Electronic Structure Calculations for Large Molecules

Cited by 287 publications

References 66 publications

Axial ligand tuning of a nonheme iron(IV)–oxo unit for hydrogen atom abstraction

Axial ligand tuning of a nonheme iron(IV)–oxo unit for hydrogen atom abstraction

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

Additivity of conformational energy: Quantum mechanical investigation of fluoro- and bromoalkanes

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