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density functional theory

Sunkyung Kim, Jin Yong Lee
The adsorption of sulfur dioxide (SO2) on pristine and modified graphyne (including boron- or nitrogen- doping and introducing a single carbon atom defect) was investigated by density functional theory calculations. The structural, electronic, and magnetic properties of graphyne were changed according to the dopant atom site of doping and vacancy. SO2 adsorption was obviously affected by modification of graphyne. SO2 weakly interacted with pristine and nitrogen-doped graphynes. Boron doping at the sp-hybridized carbon site and introducing a single carbon atom vacancy in graphyne brought about a dramatic enhancement in SO2 adsorption...
January 6, 2017: Journal of Colloid and Interface Science
Andrés Montoya-Castillo, David R Reichman
We derive a semi-analytical form for the Wigner transform for the canonical density operator of a discrete system coupled to a harmonic bath based on the path integral expansion of the Boltzmann factor. The introduction of this simple and controllable approach allows for the exact rendering of the canonical distribution and permits systematic convergence of static properties with respect to the number of path integral steps. In addition, the expressions derived here provide an exact and facile interface with quasi- and semi-classical dynamical methods, which enables the direct calculation of equilibrium time correlation functions within a wide array of approaches...
January 14, 2017: Journal of Chemical Physics
M C Kirkegaard, J Langford, J Steill, B Anderson, A Miskowiec
Uranyl fluoride (UO2F2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R3¯m symmetry. The formally closed-shell electron structure of anhydrous UO2F2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies...
January 14, 2017: Journal of Chemical Physics
Piotr de Silva, Tianyu Zhu, Troy Van Voorhis
One of the several problems that plague majority of density functional theory calculations is their inability to properly account for long-range correlations giving rise to dispersion forces. The recently proposed many-pair expansion (MPE) [T. Zhu et al., Phys. Rev. B 93, 201108(R) (2016)] is a hierarchy of approximations that systematically corrects any deficiencies of an approximate functional to finally converge to the exact energy. This is achieved by decomposing the total density into a sum of two-electron densities and accounting for successive two-, four-, six-,… electron interactions...
January 14, 2017: Journal of Chemical Physics
Sungwoo Lee, Dongwook Kim, Alex W Robertson, Euijoon Yoon, Suklyun Hong, Jisoon Ihm, Jaejun Yu, Jamie H Warner, Gun-Do Lee
Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Congyan Zhang, Ming Yu, George Anderson, Ruchira Ravinath Dharmasena, Gamini Sumanasekera
To completely understand lithium adsorption, diffusion, and capacity on the surface of phosphorene and, therefore, the prospects of phosphorene as an anode material for high-performance lithium-ion batteries (LIBs), we carried out density-functional-theory calculations and studied the lithium adsorption energy landscape, the lithium diffusion mobility, the lithium intercalation, and the lithium capacity of phosphorene. We also carried out, for the very first time, experimental measurement of the lithium capacity of phosphorene...
January 12, 2017: Nanotechnology
Hung Tan Pham, Devashis Majumdar, Jerzy Leszczynski, Minh Tho Nguyen
Geometries and electronic properties related to the ground state stabilities of several Si12M2 clusters (M: second-row (Nb and Mo) and third-row (Ta and W) transition metals, and their mixed bimetallic clusters M2: NbMo and TaW) were explored using density functional theory (DFT) computations. The computed results show that two different structural motifs emerge as the global energy minima of such clusters. They are basically singlet tubular structures in either a C2v prism ((1)A1) or a C6v antiprism ((1)A1) form...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
Atsushi Kobayashi, Ryuya Arata, Tomohiro Ogawa, Masaki Yoshida, Masako Kato
Two luminescent pyrazine-bridged dinuclear Cu(I) complexes, namely, [{Cu(PPh3)2(H2O)}(μ-MeOpyz){Cu(PPh3)2(CH3CN)}](BF4)2 and [{Cu(PPh3)2(H2O)}(μ-MeOpyz){Cu(PPh3)2(H2O)}](BF4)2 (H2O-Cu2-AN and H2O-Cu2-H2O; PPh3 = triphenylphosphine, MeOpyz = 2-methoxypyrazine), were successfully synthesized and characterized by single-crystal X-ray diffraction and luminescence measurements. X-ray analysis revealed that the water molecules are coordinated to both Cu(I) ions to form almost the same P2N1O1 coordination structure in H2O-Cu2-H2O, whereas one of the two Cu ions in H2O-Cu2-AN was coordinated by acetonitrile instead of water to form a different P2N2 coordination environment...
January 12, 2017: Inorganic Chemistry
Jinyong Liu, Xiaoge Su, Mengwei Han, Dimao Wu, Danielle L Gray, John R Shapley, Charles J Werth, Timothy J Strathmann
Recently, N,N-trans Re(O)(LN-O)2X (LN-O = monoanionic N-O chelates; X = Cl or Br prior to being replaced by solvents or alkoxides) complexes have been found to be superior to the corresponding N,N-cis isomers in the catalytic reduction of perchlorate via oxygen atom transfer. However, reported methods for Re(O)(LN-O)2X synthesis often yield only the N,N-cis complex or a mixture of trans and cis isomers. This study reports a geometry-inspired ligand design rationale that selectively yields N,N-trans Re(O)(LN-O)2Cl complexes...
January 12, 2017: Inorganic Chemistry
Arjen J de Haas, Jos Oomens, Jordy Bouwman
Energetic processing of gaseous polycyclic aromatic hydrocarbons (PAHs) plays a pivotal role in the chemistries of inter- and circumstellar environments, certain planetary atmospheres, and also in the chemistry of combustion and soot formation. Although the precursor PAH species have been extensively characterized, the products from these gaseous breakdown reactions have received far less attention. It has been particularly challenging to accurately determine their molecular structure in gas-phase experiments, where comparisons against theoretical modeling are best made...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
Furong Wang, Uli Schmidhammer, Aurélien de La Lande, Mehran Mostafavi
Oxidation by the ultra-short lived radical cation of water, H2O˙(+), can potentially take place at the interface of water and numerous heterogeneous systems involved in radiation therapy, energy and environmental industries. The oxidation processes induced by H2O˙(+) can be mimicked in highly concentrated solutions where the nearest neighbors of H2O˙(+) may be molecules other than water. The reactivity of H2O˙(+) and D2O˙(+) is probed in hydrogenated and deuterated sulfuric acid solutions of various concentrations...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
Anwar Manzoor Rana, Tahira Akbar, Muhammad Ismail, Ejaz Ahmad, Fayyaz Hussain, Ijaz Talib, Muhammad Imran, Khalid Mehmood, Khalid Iqbal, M Younus Nadeem
Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~10(2)) and no significant data degradation during endurance test of >10(4) switching cycles...
January 12, 2017: Scientific Reports
Lars Olsen, Flemming S Jørgensen, Silvia Bonomo
Aflatoxin B1 (AFB1) is a chemically intriguing compound because it has several potential sites of metabolism (SOMs) while only some of them are observed experimentally. Cytochrome P450 (CYP) 3A4 and 1A2 are the major isoforms involved in its metabolism. Here, we systematically investigate reactivity and accessibility of all possible SOMs in these two CYPs to elucidate AFB1 metabolism. Density functional theory (DFT) calculations were used to determine activation energies for each possible reaction. Aliphatic hydroxylation on position 9A and 3α are energetically favored, whereas position 9 is the preferred site for epoxidation...
January 12, 2017: Chemistry: a European Journal
Mingyue Sui, Shuangbao Li, Qingqing Pan, Guangyan Sun, Yun Geng
The upper efficiency of heterojunction organic photovoltaics depends on the increased open-circuit voltage (V oc) and short-circuit current (J sc). So, a higher lowest unoccupied molecular orbital (LUMO) level is necessary for organic acceptor material to possess higher V oc and more photons absorbsorption in the solar spectrum is needed for larger J sc. In this article, we theoretically designed some small molecule acceptors (2∼5) based on fluorene (F), benzothiadiazole, and cyano group (CN) referring to the reported acceptor material 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile (1), the crucial parameters affecting photoelectrical properties of compounds 2∼5 were evaluated by the density functional theory (DFT) and time dependent density functional theory (TDDFT) methods...
January 2017: Journal of Molecular Modeling
Jonathan Nafziger, Kaili Jiang, Adam Wasserman
The non-additive non-interacting kinetic energy (NAKE) is calculated numerically for fragments of H2, Li2, Be2, C2, N2, F2, and Na2 within partition density-functional theory (PDFT). The resulting fragments are uniquely determined and their sum reproduces the Kohn-Sham molecular density of the corresponding XC functional. We present the NAKE of these unique fragments as a function of inter-nuclear separation and compare the use of fractional orbital occupation to the usual PDFT ensemble method for treating the fragment energies and densities...
January 11, 2017: Journal of Chemical Theory and Computation
Ljupco Pejov, Manas K Panda, Taro Moriwaki, Pance Naumov
The range of unit cell orientations generated at the kink of a bent single crystal poses unsurmountable challenges with diffraction analysis and limits the insight into the molecular-scale mechanism of bending. On a plastically bent crystal of hexachlorobenzene it is demonstrated here that spatially resolved microfocus infrared spectroscopy using synchrotron radiation can be applied in conjunction with periodic density functional theory calculations to predict spectral changes or to extract information on structural changes that occur as a consequence of bending...
January 11, 2017: Journal of the American Chemical Society
Uk Sim, Joonhee Moon, Joohee Lee, JungHyun An, Hyo-Yong Ahn, Dong Jin Kim, Insu Jo, Cheolho Jeon, Seungwu Han, Byung Hee Hong, Ki Tae Nam
Photoelectrochemical cells are used to split hydrogen and oxygen from water molecules to generate chemical fuels to satisfy our ever-increasing energy demands. However, it is a major challenge to design efficient catalysts to use in the photoelectochemical process. Recently, research has focused on carbon-based catalysts, as they are non-precious and environmentally benign. Interesting advances have also been made in controlling nanostructure interfaces and in introducing new materials as catalysts in the photoelectrochemical cell...
January 11, 2017: ACS Applied Materials & Interfaces
Maria Gallego, Joaquin Calbo, Rafael M Krick-Calderon, Paula Pla, Ya-Chu Hsieh, Emilio Manuel Pérez, Yao-Ting Wu, Enrique Orti, Dirk M Guldi, Nazario Martin
The association behavior of an electron-donating, bowl-shaped, truxene-based tetrathiafulvalene (truxTTF) with two corannulene-based fullerene fragments -C32H12 and C38H14- is investigated in several solvents. Formation of 1:1 complexes is followed by absorption titrations and complemented by density functional theory (DFT) calculations. The binding constants are in the range of log Ka 2.9-3.5. DFT calculations reveal that the conformation in which the 1,3-dithiole ring of truxTTF is placed inside the concave cavity of the corannulene derivative is the most stable arrangement...
January 11, 2017: Chemistry: a European Journal
Paul Avramov, Alexander A Kuzubov, Artem V Kuklin, Hyosun Lee, Evgenia A Kovaleva, Seiji Sakai, Shiro Entani, Hiroshi Naramoto, Pavel B Sorokin
The structure of the interfaces and the mechanisms of induced spin polarization of 1D infinite and finite narrow graphene- and h-BN zigzag nanoribbons placed on a SrO-terminated La1-xSrxMnO3 (LSMO) (001) surface were studied using density functional theory (DFT) electronic structure calculations. It was found that the π-conjugated nanofragments are bonded to the LSMO(001) surface by weak disperse interactions. The types of coordination of the fragments, the strength of bonding, and the rate of spin polarization depend upon the nature of the fragments...
January 11, 2017: Journal of Physical Chemistry. A
Takuya Iwasaki, Manoharan Muruganathan, Marek E Schmidt, Hiroshi Mizuta
The transformation of systematic vacuum and hydrogen annealing effects in graphene devices on the SiO2 surface is reported based on experimental and van der Waals interaction corrected density functional theory (DFT) simulation results. Vacuum annealing removes p-type dopants and reduces charged impurity scattering in graphene. Moreover, it induces n-type doping into graphene, leading to the improvement of the electron mobility and conductivity in the electron transport regime, which are reversed by exposing to atmospheric environment...
January 11, 2017: Nanoscale
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