scholarly journals Amelioration of sintering and multi-frequency dielectric properties of Mg3B2O6: A mechanism study of nickel substitution using DFT calculation

2021 ◽  
Author(s):  
Rui Peng ◽  
Yongcheng Lu ◽  
Qin Zhang ◽  
Yuanming Lai ◽  
Guoliang Yu ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Density Functional ◽  
Dft Calculation ◽  
Simultaneous Thermal Analysis ◽  
Mechanical Analysis ◽  
Cavity Method ◽  
Mechanism Study ◽  
X Ray Diffraction ◽  
Densification Temperature ◽  
Order Degree

AbstractWith the support of density functional theory (DFT) calculation, the amelioration of sintering and dielectric properties of the Mg3B2O6 (MBO) ceramic was realized through the substitution of magnesium with nickel. The TE-mode cylindrical cavity method was used to measure the dielectric properties at different frequencies. The thermo-mechanical analysis and simultaneous thermal analysis were used to characterize the chemical and mechanical properties. The phase composition was determined through the X-ray diffraction (XRD) and Raman spectrum. The microstructure was investigated using the scanning electron microscopy (SEM). Magnesium substitution with nickel (4 mol%) could ionize the B-O bond of BO3, modify the vibration mode, improve the order degree, densify the microstructure, decrease the intrinsic densification temperature, and ameliorate the dielectric properties of the MBO ceramics. The maximum values were achieved for the ceramics with 4 mol% nickel and sintered at 1175 °C, that is, 97.2% for relative density, 72,600 GHz (10 GHz), 75,600 GHz (11.4 GHz), and 92,200 GHz (15 GHz) for Q × f, 7.1 (10 GHz), 7.01 (11.4 GHz), and 6.91 (15 GHz) for εr, and −56.3 ppm/°C for τf.

DFT Study on Two Plausible Mechanistic Routes to Pyrazolo[3,4-d]pyrimidine-4- Amines from Pyrazoloformimidate

2020 ◽  
Vol 24 (2) ◽  
pp. 216-229
Author(s):  
Amal Al-Azmi
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Dft Calculation ◽  
Reaction Pathways ◽  
Nucleophilic Attack ◽  
X Ray Diffraction ◽  
Dimroth Rearrangement ◽  
Functional Theory ◽  
X Ray ◽  
Moderate Yield

Pyrazolo[3,4-d]pyrimidine-4-amine was prepared at room temperature in a catalyst- free medium with moderate yield and characterized by spectroscopic and X-ray diffraction techniques. Two possible mechanistic routes were suggested for its formation. Route 1 entails attack by the N of the amine on the imidate carbon followed by Dimroth rearrangement after cyclization. Route 2 is the nucleophilic attack by the amine on the CN function followed by cyclization to pyrazolo[3,4-d]pyrimidine-4-amine. Density functional theory (DFT) calculation studies of the two proposed reaction pathways illustrated that the Route 2 reaction was more likely than that of Route 1.

scholarly journals Synthesis, Characterization, Absorption Properties, and Electronic Structures of Paddlewheel-Type Dirhodium(II) Tetra-μ-(n-naphthoate) Complexes: An Experimental and Theoretical Study

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 447 ◽  
Author(s):  
Yusuke Kataoka ◽  
Raiki Fukumoto ◽  
Natsumi Yano ◽  
Daiki Atarashi ◽  
Hidekazu Tanaka ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Dft Calculation ◽  
X Ray Diffraction ◽  
Absorption Properties ◽  
Thermal Stabilities ◽  
Functional Theory ◽  
X Ray ◽  
Light Region ◽  
Ligand Charge Transfer

The reactions of [Rh2(O2CCH3)4(OH2)2] with n-naphthalenecarboxylic acids (n = 1: 1-HNC, n = 2: 2-HNC) afford the dirhodium tetra-μ-(n-naphthoate) complexes [Rh2(1-NC)4] (1) and [Rh2(2-NC)4] (2), respectively. Single crystal X-ray diffraction analyses of [1(OCMe2)2] and [2(OCMe2)2], which were obtained by recrystallization from acetone (OCMe2) solutions of 1 and 2, reveal that the dirhodium cores are coordinated by four equatorially bridging naphthoate ligands and two axial OCMe2 ligands. Density functional theory (DFT) calculation confirmed that (i) the single Rh–Rh bond is formed between the two Rh ions and (ii) the electronic structures between two Rh ions in [1(OCMe2)2] and [2(OCMe2)2] are best described as π4δ2σ2δ*2π*4 and δ2π4σ2δ*2π*4, respectively. Time-dependent DFT (TDDFT) calculations clarify the absorption band characters of [1(OCMe2)2] and [2(OCMe2)2]; the former shows the bands due to d–d and metal–to–metal-ligand charge transfer (MMLCT) excitations in the visible light region, whereas the latter shows the bands due to only d–d excitations in the same region. The electrochemical properties and thermal stabilities of [1(OCMe2)2] and [2(OCMe2)2] were also investigated in this study.

scholarly journals Influence of film stretching on crystalline phases and dielectric properties of a 70/30 mol% poly(vinylidenefluoride-tetrafluoroethylene) copolymer

2020 ◽  
Vol 10 (05) ◽  
pp. 2050023
Author(s):  
Thulasinath Raman Venkatesan ◽  
Anna A. Gulyakova ◽  
Reimund Gerhard
Keyword(s):  
Dielectric Properties ◽  
Polyvinylidene Fluoride ◽  
Ferroelectric Phase ◽  
Mechanical Analysis ◽  
Dielectric Relaxation Spectroscopy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Crystalline Phases ◽  
The Stability ◽  
Dissipation Losses

Polyvinylidene fluoride (PVDF)-based copolymers with tetrafluoroethylene (P(VDF-TFE)), trifluoroethylene (P(VDF-TrFE)) or hexafluoropropylene (P(VDF-HFP)) are of strong interest due to the underlying fundamental mechanisms and the potential ferro-, pyro- and piezo-electrical applications. Their flexibility and their adaptability to various shapes are advantageous in comparison to inorganic ferroelectrics. Here, we study the influence of stretching temperature on the crystalline phases and the dielectric properties in P(VDF-TFE) films by means of Dielectric Relaxation Spectroscopy (DRS), Fourier-Transform InfraRed spectroscopy (FTIR), Wide-Angle X-ray Diffraction (WAXD), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Especially, the effect of stretching and the influence of the temperature of stretching on the mid-temperature ([Formula: see text] transition are studied in detail. The results show that stretching has a similar effect as that on PVDF, and we observe an increase in the fraction of ferroelectric [Formula: see text]-phase with a simultaneous increment in both melting point ([Formula: see text] and crystallinity ([Formula: see text] of the copolymer. While an increase in the stretching temperature does not have a profound impact on the amount of ferroelectric phase, the stability of the ferroelectric phase seems to improve — as seen in the reduction of the Full Width at Half Maximum (FWHM) of the WAXD peaks in both parallel and perpendicular directions to the molecular chain axis. The observation is also supported by the reduction of dissipation losses with an increase in stretching temperature — as seen in DRS measurements. Finally, both stretching itself and the temperature of stretching affect the various molecular processes taking place in the temperature range of the [Formula: see text] transition.

Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

2019 ◽  
Author(s):  
Simil Thomas ◽  
Hong Li ◽  
Raghunath R. Dasari ◽  
Austin Evans ◽  
William Dichtel ◽  
...  
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Density Functional ◽  
Polymer Networks ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
X Ray Diffraction ◽  
Zinc Porphyrin ◽  
Design And Synthesis ◽  
Predicted Values

<p>We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected <i>via</i> diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm<sup>2</sup>V<sup>-1</sup>s<sup>-1</sup>. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.</p>

scholarly journals Exo⇔Endo Isomerism, MEP/DFT, XRD/HSA-Interactions of 2,5-Dimethoxybenzaldehyde: Thermal, 1BNA-Docking, Optical, and TD-DFT Studies

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5970
Author(s):  
Nabil Al-Zaqri ◽  
Mohammed Suleiman ◽  
Anas Al-Ali ◽  
Khaled Alkanad ◽  
Karthik Kumara ◽  
...  
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Structural Parameters ◽  
Population Analysis ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Optical Energy Gap ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
Td Dft

The exo⇔endo isomerization of 2,5-dimethoxybenzaldehyde was theoretically studied by density functional theory (DFT) to examine its favored conformers via sp2–sp2 single rotation. Both isomers were docked against 1BNA DNA to elucidate their binding ability, and the DFT-computed structural parameters results were matched with the X-ray diffraction (XRD) crystallographic parameters. XRD analysis showed that the exo-isomer was structurally favored and was also considered as the kinetically preferred isomer, while several hydrogen-bonding interactions detected in the crystal lattice by XRD were in good agreement with the Hirshfeld surface analysis calculations. The molecular electrostatic potential, Mulliken and natural population analysis charges, frontier molecular orbitals (HOMO/LUMO), and global reactivity descriptors quantum parameters were also determined at the B3LYP/6-311G(d,p) level of theory. The computed electronic calculations, i.e., TD-SCF/DFT, B3LYP-IR, NMR-DB, and GIAO-NMR, were compared to the experimental UV–Vis., optical energy gap, FTIR, and 1H-NMR, respectively. The thermal behavior of 2,5-dimethoxybenzaldehyde was also evaluated in an open atmosphere by a thermogravimetric–derivative thermogravimetric analysis, indicating its stability up to 95 °C.

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

scholarly journals Measuring the structure and equation of state of polyethylene terephthalate at megabar pressures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Lütgert ◽  
J. Vorberger ◽  
N. J. Hartley ◽  
K. Voigt ◽  
M. Rödel ◽  
...  
Keyword(s):  
Equation Of State ◽  
Polyethylene Terephthalate ◽  
Density Functional ◽  
Equations Of State ◽  
Md Simulations ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Shock Hugoniot ◽  
Highly Correlated

AbstractWe present structure and equation of state (EOS) measurements of biaxially orientated polyethylene terephthalate (PET, $$({\hbox {C}}_{10} {\hbox {H}}_8 {\hbox {O}}_4)_n$$ ( C 10 H 8 O 4 ) n , also called mylar) shock-compressed to ($$155 \pm 20$$ 155 ± 20 ) GPa and ($$6000 \pm 1000$$ 6000 ± 1000 ) K using in situ X-ray diffraction, Doppler velocimetry, and optical pyrometry. Comparing to density functional theory molecular dynamics (DFT-MD) simulations, we find a highly correlated liquid at conditions differing from predictions by some equations of state tables, which underlines the influence of complex chemical interactions in this regime. EOS calculations from ab initio DFT-MD simulations and shock Hugoniot measurements of density, pressure and temperature confirm the discrepancy to these tables and present an experimentally benchmarked correction to the description of PET as an exemplary material to represent the mixture of light elements at planetary interior conditions.

scholarly journals Improving flexural and dielectric properties of carbon fiber epoxy composite laminates reinforced with carbon nanotubes interlayer using electrospray deposition

2020 ◽  
Vol 9 (1) ◽  
pp. 1170-1182
Author(s):  
Muhammad Razlan Zakaria ◽  
Hazizan Md Akil ◽  
Mohd Firdaus Omar ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Aslina Anjang Ab Rahman ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Dielectric Properties ◽  
Carbon Fiber ◽  
Composite Laminates ◽  
Epoxy Composite ◽  
Flexural Modulus ◽  
X Ray Diffraction ◽  
Electrospray Deposition ◽  
Ft Ir ◽  
Carbon Fiber Epoxy

AbstractThe electrospray deposition method was used to deposit carbon nanotubes (CNT) onto the surfaces of woven carbon fiber (CF) to produce woven hybrid carbon fiber–carbon nanotubes (CF–CNT). Extreme high-resolution field emission scanning electron microscopy (XHR-FESEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the woven hybrid CF–CNT. The results demonstrated that CNT was successfully and homogenously distributed on the woven CF surface. Woven hybrid CF–CNT epoxy composite laminates were then prepared and compared with woven CF epoxy composite laminates in terms of their flexural and dielectric properties. The results indicated that the flexural strength, flexural modulus and dielectric constant of the woven hybrid CF–CNT epoxy composite laminates were improved up to 19, 27 and 25%, respectively, compared with the woven CF epoxy composite laminates.

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