Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

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.

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

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.

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

6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

A general scheme for systematically modeling long-range corrected (LC) hybrid density functionals is proposed. Our resulting two LC hybrid functionals are shown to be accurate in thermochemistry, kinetics, and noncovalent interactions, when compared with common hybrid density functionals. The qualitative failures of the commonly used hybrid density functionals in some “difficult problems,” such as dissociation of symmetric radical cations and long-range charge-transfer excitations, are significantly reduced by the present LC hybrid density functionals.

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Systematic optimization of long-range corrected hybrid density functionals.

Three examples from the work of the author's research group on reactive intermediates are used to illustrate how fruitful interaction between experimental and computational chemistry may lead to the solution of problems that neither of the two methods could have solved without the other. It is shown that computational chemistry has indeed become an indispensable tool for the verification of spectroscopic assignments, the elucidation of reaction mechanisms, and the understanding of the factors that drive chemistry.

The Interplay and Synergism of Experiment and Quantum Chemistry in Research on Reactive Intermediates

Transformations induced by X-irradiation of o-phthalaldehyde (1), o-nitrobenzaldehyde (2), and o-nitrosobenzaldehyde (3) isolated in argon matrices are described. It is shown that the formyl hydrogens in 1, 2 and 3 spontaneously migrate to the respective o-substituents upon ionization. The resulting radical cations are characterized mainly by the ketene and OH stretching bands in their IR spectra.In all cases, X-irradiation led also to the formation of substantial amounts of the neutral tautomers as well as other products in the case of 2 and 3. These are thought to arise by way of the corresponding radical cations which are reneutralized by scavenging some of the electrons ejected from the matrix material upon X-irradiation.

Radiation Induced Transformations of Benzaldehydes Carrying Formyl, Nitro or Nitroso Substituents in the ortho Position.

Tris(methylidene)cyclopropane (′(3)radialene′). part 1. enthalpy of formation n and strain energy

The resonance Raman spectra of the radical cations of three deuterated derivatives of 1,3-butadiene are reported. Together with the data for the parent compound (cf.:  Keszthelyi, T.; Wilbrandt, R.; Bally, T. J. Phys. Chem. 1996, 100, 16843), 22 frequencies of totally symmetric fundamentals are available to complement 29 previously obtained IR data for the same compounds (Tang, W; Zhang, X.-L., Bally, T. J. Phys. Chem. 1993, 97, 4373) and to generate a new and improved scaled quantum mechanical force field of butadiene radical cation based on B3LYP/6-31G* second derivatives. After fitting those with 13 scaling factors, the resulting force field reproduces all 51 observed fundamental vibrations of the four isotopomers with a root-mean-square deviation of 6.03 cm-1 (10.6 cm-1 for the 11 strongly anharmonic C−H/C−D stretches, 3.92 cm-1 for the remaining 40 modes). It allows the first experimentally based prediction of the stretching force constant for the central C−C bond and corrects the previous ones for t...

Radical Cation of 1,3‐Butadiene: Resonance Raman Spectrum of Deuterated Derivatives and Improved Force Field.

The title compound (1) is prepared in situ from 5-methylenebicyclo[2.2.0]hex-2-ene by pyrolysis and subsequent photoionization in a photoelectron spectrometer or by X-ray irradiation in an Ar matrix where its electronic absorption spectrum is obtained. The results confirm earlier conjectures that the title cation exists as a distinct entity on the C7H8+ hypersurface and can be obtained photochemically from other isomeric ions or by a McLafferty rearrangement. The enthalpies of formation of 1, its precursor and the corresponding radical ions are compared to the most recent data available for other C7H8 isomers and their ions. It is shown that the thermodynamic stability of 1+ is closer to that of toluene cation than concluded on the basis of earlier results.

Thomas Bally

Papers

The Interplay and Synergism of Experiment and Quantum Chemistry in Research on Reactive Intermediates

Radiation Induced Transformations of Benzaldehydes Carrying Formyl, Nitro or Nitroso Substituents in the ortho Position.

Tris(methylidene)cyclopropane (′(3)radialene′). part 1. enthalpy of formation n and strain energy

Radical Cation of 1,3‐Butadiene: Resonance Raman Spectrum of Deuterated Derivatives and Improved Force Field.

The molecular ion of 5-methylene-1,3-cyclohexadiene: electronic absorption spectrum and revised enthalpy of formation