Ammonia Adsorption on Keggin-Type Heteropolyacid Catalysts Explored by Density Functional Quantum Chemistry Calculations

2000 ◽  
Vol 104 (15) ◽  
pp. 3556-3562 ◽  
Author(s):  
Billy B. Bardin ◽  
Robert J. Davis ◽  
Matthew Neurock
Keyword(s):  
Quantum Chemistry ◽  
Density Functional ◽  
Ammonia Adsorption ◽  
Keggin Type ◽  
Quantum Chemistry Calculations

scholarly journals Adsorption and Desorption Mechanisms of Rare Earth Elements (REEs) by Layered Double Hydroxide (LDH) Modified with Chelating Agents

2019 ◽  
Vol 9 (22) ◽  
pp. 4805 ◽  
Author(s):  
Shuang Zhang ◽  
Naoki Kano ◽  
Kenji Mishima ◽  
Hirokazu Okawa
Keyword(s):  
Rare Earth ◽  
Quantum Chemistry ◽  
Rare Earth Elements ◽  
Adsorption Capacity ◽  
Density Functional ◽  
Stable State ◽  
Experimental Result ◽  
Adsorption And Desorption ◽  
Adsorption Affinity ◽  
Quantum Chemistry Calculations

In order to obtain the adsorption mechanism and adsorption structures of Rare Earth Elements (REEs) ions adsorbed onto layered double hydroxides (LDH), the adsorption performance of LDH and ethylenediaminetetraacetic acid (EDTA) intercalated LDH for REEs was investigated by batch experiments and regeneration studies. In addition to adsorption capacity, the partition coefficient (PC) was also evaluated to assess their true performance metrics. The adsorption capacity of LDH increases from 24.9 μg·g−1 to 145 μg·g−1 for Eu, and from 20.8 μg·g−1 to 124 μg·g−1 for La by intercalating EDTA in this work; and PC increases from 45.5 μg·g−1·uM−1 to 834 μg·g−1·uM−1 for Eu, and from 33.6 μg·g−1·μM−1 to 405 μg·g−1·μM−1 for La. Comparison of the data indicates that the adsorption affinity of EDTA-intercalated LDH is better than that of precursor LDH no matter whether the concept of adsorption capacity or that of the PC was used. The prepared adsorbent was characterized by XRD, SEM-EDS and FT-IR techniques. Moreover, quantum chemistry calculations were also performed using the GAUSSIAN09 program package. In this calculation, the molecular locally stable state structures were optimized by density functional theory (DFT). Both the quantum chemistry calculations and the experimental data showed that REEs ions adsorbed by EDTA-intercalated LDH are more stable than those adsorbed by precursor LDH. Furthermore, the calculation results of adsorption and desorption rates show that adsorption rates are larger for Eu(III) than for La(III), which agrees with the experimental result that Eu(III) has a higher adsorption ability under the same conditions. The LDHs synthesized in this work have a high affinity for removing REEs ions.

Theoretical investigation of [Ru(tpy)2]2+, [Ru(tpy)(bpy)(H2O)]2+ and [Ru(tpy)(bpy)(Cl)]+ complexes in acetone revisited: Inclusion of strong spin–orbit couplings to quantum chemistry calculations

2016 ◽  
Vol 15 (01) ◽  
pp. 1650001
Author(s):  
Kenji Mishima ◽  
Takumi Kinoshita ◽  
Michitoshi Hayashi ◽  
Ryota Jono ◽  
Hiroshi Segawa ◽  
...  
Keyword(s):  
Experimental Data ◽  
Quantum Chemistry ◽  
Absorption Spectra ◽  
Density Functional ◽  
Order Perturbation ◽  
Basis Sets ◽  
Spin Orbit ◽  
First Order ◽  
Quantum Chemistry Calculations ◽  
First Order Perturbation

In the present paper, we theoretically reinvestigate structural properties, and photo-physical and chemical characteristics and electronic absorption spectra of three kinds of ruthenium polypyridyl complexes [Ru(tpy)[Formula: see text], [Ru(tpy)(bpy)(H2O)][Formula: see text], and [Ru(tpy)(bpy)(Cl)][Formula: see text] complexes in acetone (tpy[Formula: see text]2,2[Formula: see text],2[Formula: see text]-terpyridine and bpy[Formula: see text]2,2[Formula: see text]-bipyridine). In particular, the experimental absorption spectra of these complexes are revisited theoretically in detail and are simulated using the first-order perturbation theory based on time-dependent density functional theory (TD-DFT) where the first-order perturbation term is the spin–orbit (SO) coupling Hamiltonian, and quantum chemistry calculations based on various functionals and basis sets. It was found that in general the theory including SO coupling can reproduce experimental data better than the simple quantum chemistry calculation neglecting SO coupling, which indicates that SO coupling is very important to understand the optical features of these complexes and that therefore the mixing between singlet and triplet states is strong due to the large SO coupling constant of Ru atom involved in these complexes. This suggests the fact that the disagreement between the experimental and calculated absorption spectra was found in TDB3LYP/(SDD with triple-[Formula: see text] for Ru and 6-31G* for others) [Jakubikova EJ et al., Inorg Chem 48:10720, 2009] can be tracked down to the neglect of SO couplings. It was also found that the choice of the DFT functionals and basis sets is crucial for a good theoretical reproduction of experimental data.

scholarly journals The Quantum-Chemistry Calculations of Electronic Structure of Boron Nitride Nanocrystals with Density Functional Theory Realization

2019 ◽  
Vol 62 (1) ◽  
pp. 11-12
Author(s):  
Dilshod D. Nematov ◽  
Amondullo S. Burhonzoda ◽  
Mirzoaziz A. Khusenov ◽  
Kholmirzo T. Kholmurodov ◽  
Medhat A.A. Ibrahim
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Boron Nitride ◽  
Quantum Chemistry ◽  
Density Functional ◽  
Functional Theory ◽  
Quantum Chemistry Calculations

A new look at two polymorphic crystal structures of dibenzoylmethane: relationship between the crystal packing and the hydrogen atom position revealed by quantum chemistry and quantum crystallography methods

2020 ◽  
Vol 76 (6) ◽  
pp. 957-966
Author(s):  
Sławomir Wojtulewski ◽  
Jakub Wladyslaw Strawa ◽  
Michal Tomczyk ◽  
Magdalena Gawel ◽  
Krzysztof Brzezinski
Keyword(s):  
Quantum Chemistry ◽  
Crystal Structures ◽  
Density Functional ◽  
Tautomeric Form ◽  
Crystal Packing ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Quantum Chemistry Calculations ◽  
Quantum Crystallography ◽  
Atom Position

Chalcones, including dibenzoylmethane, are an important subgroup of natural polyphenolic compounds that exhibit a wide spectrum of pharmacological and industrial applications. Dibenzoylmethane was isolated from Hottonia palustris L. (Primulaceae). The compound was crystallized in two polymorphic forms: in monoclinic space group P21/c and orthorhombic space group Pbca. Crystal structures of the polymorphs were solved and refined against diffraction data measured at 100 and 293 K. In both crystal structures, the chalcone occurs in its keto–enol tautomeric form with the hydroxyl H atom mutually bound by two oxygen atoms rather than covalently attached to a particular oxygen atom. To explain this phenomenon in more detail, density functional theory and quantum theory of atoms in molecules based quantum chemistry calculations were applied. Additionally, high-resolution experimental data of very high quality measured for the monoclinic and orthorhombic crystals at 100 K allowed the engagement of the quantum crystallography method, based on Hirshfeld atom refinement, to determine the position of each individual H atom. It is suggested that the presence of the particular tautomeric form of dibenzoylmethane with a centred H atom position results from the π-stacking interaction between the phenyl ring and the malondialdehyde quasi-ring causes delocalization of the electron density in the latter.

Introduction to Relativistic Quantum Chemistry

2007 ◽  
Author(s):  
Kenneth G. Dyall ◽  
Knut Faegri
Keyword(s):  
Dirac Equation ◽  
Quantum Chemistry ◽  
Relativistic Theory ◽  
Density Functional ◽  
Relativistic Quantum ◽  
Relativistic Effects ◽  
Basis Sets ◽  
Spin Orbit ◽  
Approximate Methods ◽  
Nonrelativistic Theory

This book provides an introduction to the essentials of relativistic effects in quantum chemistry, and a reference work that collects all the major developments in this field. It is designed for the graduate student and the computational chemist with a good background in nonrelativistic theory. In addition to explaining the necessary theory in detail, at a level that the non-expert and the student should readily be able to follow, the book discusses the implementation of the theory and practicalities of its use in calculations. After a brief introduction to classical relativity and electromagnetism, the Dirac equation is presented, and its symmetry, atomic solutions, and interpretation are explored. Four-component molecular methods are then developed: self-consistent field theory and the use of basis sets, double-group and time-reversal symmetry, correlation methods, molecular properties, and an overview of relativistic density functional theory. The emphases in this section are on the basics of relativistic theory and how relativistic theory differs from nonrelativistic theory. Approximate methods are treated next, starting with spin separation in the Dirac equation, and proceeding to the Foldy-Wouthuysen, Douglas-Kroll, and related transformations, Breit-Pauli and direct perturbation theory, regular approximations, matrix approximations, and pseudopotential and model potential methods. For each of these approximations, one-electron operators and many-electron methods are developed, spin-free and spin-orbit operators are presented, and the calculation of electric and magnetic properties is discussed. The treatment of spin-orbit effects with correlation rounds off the presentation of approximate methods. The book concludes with a discussion of the qualitative changes in the picture of structure and bonding that arise from the inclusion of relativity.

Novel thermally activated delayed fluorescence materials by high-throughput virtual screening: going beyond donor–acceptor design

2021 ◽  
Vol 9 (9) ◽  
pp. 3324-3333 ◽  
Author(s):  
Ke Zhao ◽  
Ömer H. Omar ◽  
Tahereh Nematiaram ◽  
Daniele Padula ◽  
Alessandro Troisi
Keyword(s):  
Virtual Screening ◽  
Quantum Chemistry ◽  
High Throughput ◽  
Delayed Fluorescence ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Quantum Chemistry Calculations ◽  
Donor Acceptor ◽  
Molecular Semiconductors ◽  
High Throughput Virtual Screening

125 potential TADF candidates are identified through quantum chemistry calculations of 700 molecules derived from a database of 40 000 molecular semiconductors. Most of them are new and some do not belong to the class of donor–acceptor molecules.

scholarly journals Doping the Buckminsterfullerene by Substitution: Density Functional Theory Studies of C59X (X = B, N, Al, Si, P, Ga, Ge, and As)

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Hongcun Bai ◽  
Wenxin Ji ◽  
Xiangyu Liu ◽  
Liqiong Wang ◽  
Nini Yuan ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Physical Properties ◽  
Density Functional ◽  
Dielectric Constants ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Relative Stabilities ◽  
As Doping ◽  
Quantum Chemistry Calculations ◽  
Heteroatom Substitution

The heterofullerenes C59X (X = B, N, Al, Si, P, Ga, Ge, and As) were investigated by quantum chemistry calculations based on density functional theory. These hybrid cages can be seen as doping the buckminsterfullerene by heteroatom substitution. The geometrical structures, relative stabilities, electronic properties, vibrational frequencies, dielectric constants, and aromaticities of the doped cages were studied systemically and compared with those of the pristine C60cage. It is found that the doped cages with different heteroatoms exhibit various electronic, vibrational, and aromatic properties. These results imply the possibility to modulate the physical properties of these fullerene-based materials by tuning substitution elements.

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