Charged domain boundaries stabilized by translational symmetry breaking in the hybrid improper ferroelectric Ca3–xSrxTi2O7

AbstractCharged domain walls and boundaries in ferroelectric materials display distinct phenomena, such as an increased conductivity due to the accumulation of bound charges. Here, we report the electron microscopy observations of atomic-scale arrangements at charged domain boundaries in the hybrid improper ferroelectric Ca2.46Sr0.54Ti2O7. Like in the prototype improper ferroelectric YMnO3, we find that charged domain boundaries in Ca2.46Sr0.54Ti2O7 correspond to out-of-phase boundaries, which separate adjacent domains with a fractional translational shift of the unit cell. In addition, our results show that strontium ions are located at charged domain boundaries. The out-of-phase boundary structure may decrease the polarization charge at the boundary because of the ferrielectric nature of Ca2.46Sr0.54Ti2O7, thereby promoting the stabilization of the charged state. By combining atomic-resolution imaging and density-functional theory calculations, this study proposes an unexplored stabilization mechanism of charged domain boundaries and structural defects accompanying out-of-phase translational shifts.

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DFT Studies of Graphene-Functionalised Derivatives of Capecitabine

Zeitschrift für Naturforschung A ◽

10.1515/zna-2017-0290 ◽

2017 ◽

Vol 72 (12) ◽

pp. 1131-1138 ◽

Cited By ~ 1

Author(s):

Mehdi Aramideh ◽

Mahmoud Mirzaei ◽

Ghadamali Khodarahmi ◽

Oğuz Gülseren

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Atomic Scale ◽

Phase System ◽

Molecular Models ◽

Functional Theory ◽

Atomic Properties ◽

Scale Properties ◽

Derivatives Of

AbstractCancer is one of the major problems for so many people around the world; therefore, dedicating efforts to explore efficient therapeutic methodologies is very important for researchers of life sciences. In this case, nanostructures are expected to be carriers of medicinal compounds for targeted drug design and delivery purposes. Within this work, the graphene (Gr)-functionalised derivatives of capecitabine (CAP), as a representative anticancer, have been studied based on density functional theory calculations. Two different sizes of Gr molecular models have been used for the functionalisation of CAP counterparts, CAP-Gr3 and CAP-Gr5, to explore the effects of Gr-functionalisation on the original properties of CAP. All singular and functionalised molecular models have been optimised and the molecular and atomic scale properties have been evaluated for the optimised structures. Higher formation favourability has been obtained for CAP-Gr5 in comparison with CAP-Gr3 and better structural stability has been obtained in the water-solvated system than the isolated gas-phase system for all models. The CAP-Gr5 model could play a better role of electron transferring in comparison with the CAP-Gr3 model. As a concluding remark, the molecular properties of CAP changed from singular to functionalised models whereas the atomic properties remained almost unchanged, which is expected for a carrier not to use significant perturbations to the original properties of the carried counterpart.

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Atomic-Scale Understanding of Structure and Properties of Complex Pyrophosphate Crystals by First-Principles Calculations

Applied Sciences ◽

10.3390/app9050840 ◽

2019 ◽

Vol 9 (5) ◽

pp. 840 ◽

Cited By ~ 1

Author(s):

Redouane Khaoulaf ◽

Puja Adhikari ◽

Mohamed Harcharras ◽

Khalid Brouzi ◽

Hamid Ez-Zahraouy ◽

...

Keyword(s):

First Principles ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Atomic Scale ◽

Functional Theory ◽

Local Structures ◽

Cationic Group ◽

Metallic Cations ◽

Bonding And Bridging ◽

Open Question

The electronic structure and mechanical and optical properties of five pyrophosphate crystals with very complex structures are studied by first principles density functional theory calculations. The results show the complex interplay of the minor differences in specific local structures and compositions can result in large differences in reactivity and interaction that are rare in other classes of inorganic crystals. These are discussed by dividing the pyrophosphate crystals into three structural units. H2P2O7 is the most important and dominating unit in pyrophosphates. The other two are the influential cationic group with metals and water molecules. The strongest P-O bond in P2O5 is the strongest bond for crystal cohesion, but O-H and N-H bonds also play an important part. Different type of bonding between O and H atoms such as O-H, hydrogen bonding, and bridging bonds are present. Metallic cations such as Mg, Zn, and Cu form octahedral bonding with O. The water molecule provides the unique H∙∙∙O bonds, and metallic elements can influence the structure and bonding to a certain extent. The two Cu-containing phosphates show the presence of narrow metallic bands near the valence band edge. All this complex bonding affects their physical properties, indicating that fundamental understanding remains an open question.

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Subsurface cation vacancy stabilization of the magnetite (001) surface

Science ◽

10.1126/science.1260556 ◽

2014 ◽

Vol 346 (6214) ◽

pp. 1215-1218 ◽

Cited By ~ 133

Author(s):

R. Bliem ◽

E. McDermott ◽

P. Ferstl ◽

M. Setvin ◽

O. Gamba ◽

...

Keyword(s):

Iron Oxides ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Atomic Scale ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Material Interface ◽

Functional Theory ◽

Ordered Array ◽

Low Energy Electron

Iron oxides play an increasingly prominent role in heterogeneous catalysis, hydrogen production, spintronics, and drug delivery. The surface or material interface can be performance-limiting in these applications, so it is vital to determine accurate atomic-scale structures for iron oxides and understand why they form. Using a combination of quantitative low-energy electron diffraction, scanning tunneling microscopy, and density functional theory calculations, we show that an ordered array of subsurface iron vacancies and interstitials underlies the well-known (2×2)R45° reconstruction of Fe3O4(001). This hitherto unobserved stabilization mechanism occurs because the iron oxides prefer to redistribute cations in the lattice in response to oxidizing or reducing environments. Many other metal oxides also achieve stoichiometry variation in this way, so such surface structures are likely commonplace.

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The Role of SiH3 Diffusion in Determining the Surface Smoothness of Plasma-Deposited Amorphous Si Thin Films: An Atomic-Scale Analysis

MRS Proceedings ◽

10.1557/proc-862-a3.2 ◽

2005 ◽

Vol 862 ◽

Author(s):

Mayur S. Valipa ◽

Tamas Bakos ◽

Eray S. Aydil ◽

Dimitrios Maroudas

Keyword(s):

Thin Films ◽

Density Functional ◽

Activation Barrier ◽

Density Functional Theory Calculations ◽

Atomic Scale ◽

Functional Theory ◽

Weak Adsorption ◽

Dynamics Simulations ◽

Hydrogenated Amorphous

AbstractDevice-quality hydrogenated amorphous silicon (a-Si:H) thin films grown under conditions where the SiH3 radical is the dominant deposition precursor are remarkably smooth, as the SiH3 radical is very mobile and fills surface valleys during its diffusion on the a-Si:H surface. In this paper, we analyze atomic-scale mechanisms of SiH3 diffusion on a-Si:H surfaces based on molecular-dynamics simulations of SiH3 radical impingement on surfaces of a-Si:H films. The computed average activation barrier for radical diffusion on a-Si:H is 0.16 eV. This low barrier is due to the weak adsorption of the radical onto the a-Si:H surface and its migration predominantly through overcoordination defects; this is consistent with our density functional theory calculations on crystalline Si surfaces. The diffusing SiH3 radical incorporates preferentially into valleys on the a-Si:H surface when it transfers an H atom and forms a Si-Si backbond, even in the absence of dangling bonds.

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Bottom-up Fabrication and Atomic-scale Characterization of Triply-linked, Laterally π-Extended Porphyrin Nanotapes

10.26434/chemrxiv.14130596.v2 ◽

2021 ◽

Author(s):

Qiang Sun ◽

Luis M. Mateos ◽

Roberto Robles ◽

Nicolas Lorente ◽

Pascal Ruffieux ◽

...

Keyword(s):

Electronic Properties ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Molecular Wires ◽

Atomic Scale ◽

Functional Theory ◽

Structural And Electronic Properties ◽

Scale Characterization ◽

Low Solubility

<p>Porphyrin nanotapes (Por NTs) have attracted vast interest as potential molecular wires thanks to their exceptional electronic properties. Recently, Por NTs have been synthesized by solution-based methods, demonstrating high versatility and great potential for technological applications. However, their synthesis is tedious and their characterization limited by low solubility and stability. Here, we report the first example of meso-meso triply-fused Por NTs, which are prepared from a readily available Por precursor through a two-step synthesis on Au(111). The structural and electronic properties of individual Por NTs are addressed, both on Au(111) and on a thin insulating NaCl layer, by high-resolution scanning probe microscopy/spectroscopy complemented by density functional theory calculations.<br></p>

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Synthesis and characterization of quaternary La(Sr)S–TaS2 misfit-layered nanotubes

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.10.111 ◽

2019 ◽

Vol 10 ◽

pp. 1112-1124 ◽

Cited By ~ 3

Author(s):

Marco Serra ◽

Erumpukuthickal Ashokkumar Anumol ◽

Dalit Stolovas ◽

Iddo Pinkas ◽

Ernesto Joselevich ◽

...

Keyword(s):

Density Functional ◽

Morphological Characteristics ◽

Density Functional Theory Calculations ◽

High Resolution Electron Microscopy ◽

Atomic Scale ◽

Layered Compounds ◽

Functional Theory ◽

Resolution Electron ◽

Structural Aspects

Misfit-layered compounds (MLCs) are formed by the combination of different lattices and exhibit intriguing structural and morphological characteristics. MLC Sr x La1− x S–TaS2 nanotubes with varying Sr composition (10, 20, 40, and 60 Sr atom %, corresponding to x = 0.1, 0.2, 0.4 and 0.6, respectively) were prepared in the present study and systematically investigated using a combination of high-resolution electron microscopy and spectroscopy. These studies enable detailed insight into the structural aspects of these phases to be gained at the atomic scale. The addition of Sr had a significant impact on the formation of the nanotubes with higher Sr content, leading to a decrease in the yield of the nanotubes. This trend can be attributed to the reduced charge transfer between the rare earth/S unit (La x Sr1− x S) and the TaS2 layer in the MLC which destabilizes the MLC lattice. The influence of varying the Sr content in the nanotubes was systematically studied using Raman spectroscopy. Density functional theory calculations were carried out to support the experimental observations.

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Crystal and electronic facet analysis of ultrafine Ni2P particles by solid-state NMR nanocrystallography

Nature Communications ◽

10.1038/s41467-021-24589-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Wassilios Papawassiliou ◽

José P. Carvalho ◽

Nikolaos Panopoulos ◽

Yasser Al Wahedi ◽

Vijay Kumar Shankarayya Wadi ◽

...

Keyword(s):

Electronic Structure ◽

Solid State ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Atomic Scale ◽

Crystal Nucleation ◽

Functional Theory ◽

Colloidal Chemistry ◽

Facet Analysis ◽

Knight Shifts

AbstractStructural and morphological control of crystalline nanoparticles is crucial in the field of heterogeneous catalysis and the development of “reaction specific” catalysts. To achieve this, colloidal chemistry methods are combined with ab initio calculations in order to define the reaction parameters, which drive chemical reactions to the desired crystal nucleation and growth path. Key in this procedure is the experimental verification of the predicted crystal facets and their corresponding electronic structure, which in case of nanostructured materials becomes extremely difficult. Here, by employing 31P solid-state nuclear magnetic resonance aided by advanced density functional theory calculations to obtain and assign the Knight shifts, we succeed in determining the crystal and electronic structure of the terminating surfaces of ultrafine Ni2P nanoparticles at atomic scale resolution. Our work highlights the potential of ssNMR nanocrystallography as a unique tool in the emerging field of facet-engineered nanocatalysts.

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DFT Examination of Electronic and Structural Features of Favipiravir for Iron Chelation

Biointerface Research in Applied Chemistry ◽

10.33263/briac124.50815088 ◽

2021 ◽

Vol 12 (4) ◽

pp. 5081-5088

Keyword(s):

Mechanism Of Action ◽

Density Functional ◽

Energy Levels ◽

Iron Chelation ◽

Density Functional Theory Calculations ◽

Structural Features ◽

Atomic Scale ◽

Functional Theory ◽

Complex Models ◽

Atomic Descriptors

Density functional theory calculations were performed to examine electronic and structural features of favipiravir (Fav) for iron (Fe) chelation. Fav was well known for the possible medication of COVID-19; however, its mechanism of action has still been a challenging issue. Therefore, this work was done to provide information regarding the possible action of Fav for participating in the Fe chelation process. To this aim, various types of molecular and atomic descriptors were obtained to discuss the topic of this work. Obtained values of energies indicated different levels of stability for pure Fav compounds, in which such variations were also found for FavFe complexes. Molecular orbital-related features showed a different tendency to contribute to reactions for both pure and complex Fav models, in which changes of the energy levels of molecular orbitals raise the detection function of Fe for Fav compounds. Atomic-scale features also indicated direct and indirect roles of atomic sites for formations of FavFe complex models. As a consequence, the idea of Fe chelation by Fav compound was affirmed regarding the obtained results with providing detailed information for investigating the mechanism of action of Fav in treatment of COVID-19.

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Bottom-up Fabrication and Atomic-scale Characterization of Triply-linked, Laterally π-Extended Porphyrin Nanotapes

10.26434/chemrxiv.14130596.v1 ◽

2021 ◽

Author(s):

Qiang Sun ◽

Luis M. Mateos ◽

Roberto Robles ◽

Nicolas Lorente ◽

Pascal Ruffieux ◽

...

Keyword(s):

Electronic Properties ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Molecular Wires ◽

Atomic Scale ◽

Functional Theory ◽

Structural And Electronic Properties ◽

Scale Characterization ◽

Low Solubility

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Non-Covalent Functionalisation of C30 Fullerene by Pyrrole-n-Carboxylic Acid (n=2, 3): Density Functional Theory Studies

Zeitschrift für Naturforschung A ◽

10.1515/zna-2017-0233 ◽

2017 ◽

Vol 73 (1) ◽

pp. 51-56

Author(s):

Kun Harismah ◽

Mahmoud Mirzaei ◽

Nahid Ghasemi ◽

Mohammad Nejati

Keyword(s):

Density Functional Theory ◽

Carboxylic Acid ◽

Density Functional ◽

Spherical Shape ◽

Density Functional Theory Calculations ◽

Coupling Constants ◽

Atomic Scale ◽

Functional Theory ◽

Quadrupole Coupling ◽

Non Covalent Interactions

AbstractFor functionalisation of a representative C30 fullerene nanostructure by pyrrole-n-carboxylic acid (PnCA; n=2, 3) their stabilities and properties were investigated based on density functional theory calculations. Parallel calculations were also done for C60 fullerene as evidence for comparing the results. Non-covalent interactions are considered to make the functionalised structures. In contrast with the spherical shape of C60, the shape of C30 fullerene is elliptical; therefore, the functionalisation processes were done for both axial and equatorial elliptical positions (AC30 and EC30). The results indicated that both the positions of C30 have almost equivalent chances to be functionalised by PnCA; but functionalisation by P2CA is slightly more favourable than P3CA, either for C60. The illustrated molecular orbitals’ distributions indicated that the direction of charge transfer could be considered from PnCA counterparts to fullerene counterparts. The molecular properties indicated more reactivity for C30 than for C60 fullerene. Finally, the atomic scale quadrupole coupling constants indicated different roles for N and O atoms of PnCA in the functionalised models.

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