scholarly journals Can the results of quantum refinement be improved with a continuum-solvation model?

2021 ◽  
Vol 77 (6) ◽  
Author(s):  
Justin Bergmann ◽  
Esko Oksanen ◽  
Ulf Ryde
Keyword(s):  
High Dielectric Constant ◽  
Computation Time ◽  
Real Space ◽  
Solvation Model ◽  
Interesting Part ◽  
Powerful Approach ◽  
Constant E ◽  
High Dielectric ◽  
Low Charge ◽  
The Continuum

Quantum refinement has repeatedly been shown to be a powerful approach to interpret and improve macromolecular crystal structures, allowing for the discrimination between different interpretations of the structure, regarding the protonation states or the nature of bound ligands, for example. In this method, the empirical restraints, used to supplement the crystallographic raw data in standard crystallographic refinement, are replaced by more accurate quantum mechanical (QM) calculations for a small, but interesting, part of the structure. Previous studies have shown that the results of quantum refinement can be improved if the charge of the QM system is reduced by adding neutralizing groups. However, this significantly increases the computation time for the refinement. In this study, we show that a similar improvement can be obtained if the original highly charged QM system is instead immersed in a continuum solvent in the QM calculations. The best results are typically obtained with a high dielectric constant (ɛ). The continuum solvent improves real-space Z values, electron-density difference maps and strain energies, and it normally does not affect the discriminatory power of the calculations between different chemical interpretations of the structure. However, for structures with a low charge in the QM system or with a low crystallographic resolution (>2 Å), no improvement of the structures is seen.

scholarly journals Materials with high dielectric permeability on the basis of spontaneously polarized systems, lithium conductors and transition metal oxides

2021 ◽  
pp. 67-78
Author(s):  
Anatolii G. Belous ◽  
◽  
Oleg I. V'yunov ◽  
Oleg Z. Yanchevskii ◽  
Leonid L. Kovalenko ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
High Dielectric Constant ◽  
Wide Frequency Range ◽  
Dielectric Losses ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Low Frequencies ◽  
Low Dielectric ◽  
Constant E ◽  
High Dielectric

Materials with a high dielectric constant (e > 1000) based on complex oxides of spontaneously polarized systems, lithium-conducting systems, and oxides of transition metals were studied. It was shown in dielectric ceramics Ba(Ti,Sn)O3 the absence of significant dispersion of dielectric parameters (e and tg δ) in a wide frequency range from 1 to 105 Hz. The introduction of MnO2 and Al2O3-SiO2-TiO2 improves dielectric parameters and reduces sintering temperature. Obtained ceramic materials are characterized by high dielectric constant values e ~ 13000–16000 and low dielectric losses tg d ~ 0.05–0.06 (at 1 MHz). Synthesized solid solutions of La0.5Li0.5-xNaxTiO3 system, where x = 0 and 0.1, have high values e¢ > 104 at low frequencies (f ≤ 10 Hz). Dielectric properties of these materials are determined by the lithium ions mobility that increases with the rise of sodium content by increasing bottleneck size and decreases by the number of lithium vacancies reduction. The disadvantage of such materials is the decrease in dielectric constant with frequency increase. It was found that the ceramic СaСu3Тi4–xAlxО12-y-0.5xFy with x/y = 0.04/0.04 after sintering for 10 h is characterized by dielectric parameters: e¢ » 71000 (1 kHz) and tg d » 0.047. Introduction of aluminum (x/y = 0.04/0) or fluorine (0/0.08) in CCTO reduces dielectric losses (tg d » 0.044). The advantages of this type of material are a wide frequency range of high dielectric constant and relatively low dielectric loss. Synthesized materials can be used for the development of ceramic capacitors with high characteristics.

Enhanced performance of supercapacitors by constructing a “mini parallel-plate capacitor” in an electrode with high dielectric constant materials

2020 ◽  
Vol 8 (32) ◽  
pp. 16661-16668
Author(s):  
Huayao Tu ◽  
Shouzhi Wang ◽  
Hehe Jiang ◽  
Zhenyan Liang ◽  
Dong Shi ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Carbon Fiber ◽  
Parallel Plate ◽  
Sandwich Structure ◽  
High Dielectric Constant ◽  
Parallel Plate Capacitor ◽  
Plate Capacitor ◽  
Fiber Metal ◽  
High Dielectric ◽  
Mini Plate

The carbon fiber/metal oxide/metal oxynitride layer sandwich structure is constructed in the electrode to form a mini-plate capacitor. High dielectric constant metal oxides act as dielectric to increase their capacitance.

Skin–core structured fluorinated MWCNTs: a nanofiller towards a broadband dielectric material with a high dielectric constant and low dielectric loss

2018 ◽  
Vol 6 (9) ◽  
pp. 2370-2378 ◽  
Author(s):  
Yang Liu ◽  
Cheng Zhang ◽  
Benyuan Huang ◽  
Xu Wang ◽  
Yulong Li ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
High Dielectric Constant ◽  
Dielectric Material ◽  
Epoxy Composite ◽  
Low Dielectric ◽  
High Dielectric

A novel skin–core structured fluorinated MWCNT nanofiller was prepared to fabricate epoxy composite with broadband high dielectric constant and low dielectric loss.

Atomistic prediction on the configuration- and temperature-dependent dielectric constant of Be0.25Mg0.75O superlattice as a high-κ dielectric layer

2021 ◽  
Author(s):  
Gyuseung Han ◽  
In Won Yeu ◽  
Kun Hee Ye ◽  
Seung-Cheol Lee ◽  
Cheol Seong Hwang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dft Calculations ◽  
Bond Length ◽  
Dielectric Layer ◽  
Room Temperature ◽  
High Dielectric Constant ◽  
Temperature Dependent ◽  
High Dielectric

Through DFT calculations, a Be0.25Mg0.75O superlattice having long apical Be–O bond length is proposed to have a high bandgap (>7.3 eV) and high dielectric constant (∼18) at room temperature and above.

scholarly journals Defect Processes in Halogen Doped SnO2

2021 ◽  
Vol 11 (2) ◽  
pp. 551
Author(s):  
Petros-Panagis Filippatos ◽  
Nikolaos Kelaidis ◽  
Maria Vasilopoulou ◽  
Dimitris Davazoglou ◽  
Alexander Chroneos
Keyword(s):  
Electronic Properties ◽  
Tin Oxide ◽  
Density Functional ◽  
Structural Changes ◽  
High Dielectric Constant ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Optical And Electronic Properties ◽  
High Dielectric ◽  
Gap States

In the present study, we performed density functional theory calculations (DFT) to investigate structural changes and their impact on the electronic properties in halogen (F, Cl, Br, and I) doped tin oxide (SnO2). We performed calculations for atoms intercalated either at interstitial or substitutional positions and then calculated the electronic structure and the optical properties of the doped SnO2. In all cases, a reduction in the bandgap value was evident, while gap states were also formed. Furthermore, when we insert these dopants in interstitial and substitutional positions, they all constitute a single acceptor and donor, respectively. This can also be seen in the density of states through the formation of gap states just above the valence band or below the conduction band, respectively. These gap states may contribute to significant changes in the optical and electronic properties of SnO2, thus affecting the metal oxide’s suitability for photovoltaics and photocatalytic devices. In particular, we found that iodine (I) doping of SnO2 induces a high dielectric constant while also reducing the oxide’s bandgap, making it more efficient for light-harvesting applications.

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