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.

The reaction of acetylene (Ac) with its radical cation (Ac•+) is studied at the CCSD(T)/cc-pVTZ//QCISD/6-31G* level of theory and by the B3LYP/6-31G* density functional method. Contrary to earlier claims, we find that vertical ionization of the neutral acetylene dimer leads to a bound state which relaxes to a T-shaped ion−molecule complex 8.3 kcal/mol below the separated fragments. Once Ac and Ac•+ have approached to less than an ≈3 A center to center distance, spin and charge begin to delocalize and the complex collapses smoothly to the cyclobutadiene radical cation (CB) via a linear complex (LC1) and/or a cyclopropenylcarbene cation (CC). Rearrangements to other stable C4H4•+ isomers require H shifts which are promoted by localization of the positive charge on one C atom. From LC1 this leads directly to the transition state LC2 for formation of a pivotal intermediate, H2CCCHCH•+ (methyleneallene, MA), which in turn collapses with Ea ≈ 3 kcal/mol to the methylenecyclopropene radical cation (MCP), the mos...

The C4H4•+ Potential Energy Surface. 3. The Reaction of Acetylene with Its Radical Cation

A high-resolution photoelectron spectrum of p-benzoquinone in the low energy (9.5–11.5 eV) region is reported and analyzed with the aid of simulations based on high-level ab initio calculations. The results generally support the notion that the two prominent spectral features in this region are each due to a pair of final ion states. The lower energy feature beginning near 10 eV is due to oxygen lone-pair ionizations, while that beginning near 11 eV comes from π electron removal. Contrary to previous interpretations of the spectrum, however, the results of this study indicate that the two π states are nearly degenerate, with the strongest peak in the photoelectron spectrum representing a convolution of the corresponding pair of 0–0 ionizations.

On the photoelectron spectrum of p-benzoquinone

Calculations on Open-Shell Molecules: A Beginner's Guide

Ar matrix photolysis of 1- and 2-naphthyl azides 3 and 4 at 313 nm initially affords the singlet naphthyl nitrenes, (1)()1 and (1)()2. Relaxation to the corresponding lower energy, persistent triplet nitrenes (3)()1 and (3)()2 competes with cyclization to the azirines 15 and 18, which can also be formed photochemically from the triplet nitrenes. On prolonged irradiation, the azirines can be converted to the seven-membered cyclic ketenimines 10 and 13, respectively, as described earlier by Dunkin and Thomson. However, instead of the o-quinoid ketenimines 16 and 19, which are the expected primary ring-opening products of azirines 15 and 18, respectively, we observed their novel bond-shift isomers 17 and 20, which may be formally regarded as cyclic nitrile ylides. The existence of such ylidic heterocumulenes has been predicted previously, but this work provides the first experimental observation of such species. The factors which are responsible for the special stability of the ylidic species 17 and 20 are discussed.

The Rearrangements of Naphthylnitrenes: UV/Vis and IR Spectra of Azirines, Cyclic Ketenimines, and Cyclic Nitrile Ylides

The excited-state dynamics of the radical cations of perylene (PE•+), tetracene (TE•+), and thianthrene (TH•+), as well as the radical anions of anthraquinone (AQ•-) and tetracenequinone (TQ•-), formed by γ irradiation in low-temperature matrices (PE•+, TH•+, AQ•-, and TQ•-) or by oxidation in sulfuric acid (PE•+, TE•+, and TH•+) have been investigated using ultrafast pump−probe spectroscopy The longest ground-state recovery time measured was 100 ps The excited-state lifetime of PE•+ is substantially longer in low-temperature matrices than in H2SO4, where the effects of perdeuteration and of temperature on the ground-state recovery dynamics indicate that internal conversion is not the major decay channel of PE•+* The data suggest that both PE•+* and TE•+* decay mainly through an intermolecular quenching process, most probably a reversible charge transfer reaction Contrarily to AQ•-*, TQ•-* exhibits an emission in the visible which, according to theoretical calculations, occurs from an upper excited state

Thomas Bally

Papers

The C4H4•+ Potential Energy Surface. 3. The Reaction of Acetylene with Its Radical Cation

On the photoelectron spectrum of p-benzoquinone

Calculations on Open-Shell Molecules: A Beginner's Guide

The Rearrangements of Naphthylnitrenes: UV/Vis and IR Spectra of Azirines, Cyclic Ketenimines, and Cyclic Nitrile Ylides

Excited-State Dynamics of Organic Radical Ions in Liquids and in Low-Temperature Matrices