Feasibility of Predicting Static Dielectric Constants of Polymer Materials: A Density Functional Theory Method

The rapid development of electronic devices with high integration levels, a light weight, and a multifunctional performance has fostered the design of novel polymer materials with low dielectric constants, which is crucial for the electronic packaging and encapsulation of these electronic components. Theoretical studies are more efficient and cost-effective for screening potential polymer materials with low dielectric constants than experimental investigations. In this study, we used a molecular density functional theory (DFT) approach combined with the B3LYP functional at the 6-31+G(d, p) basis set to validate the feasibility of predicting static dielectric constants of the polymer materials. First, we assessed the influence of the basis sets on the polarizability. Furthermore, the changes of polarizability, polarizability per monomer unit, and differences in polarizability between the consecutive polymer chains as a function of the number of monomers were summarized and discussed. We outlined a similar behavior for the volume of the polymers as well. Finally, we simulated dielectric constants of three typical polymer materials, polyethylene (PE), polytetrafluoroethylene (PTFE), and polystyrene (PS), by combining with the Clausius–Mossotti equation. The simulated results showed excellent agreement with experimental data from the literature, suggesting that this theoretical DFT method has great potential for the molecular design and development of novel polymer materials with low dielectric constants.

Molecular Interactions and Dielectric Relaxation in the Mixtures of Amines with 2-Fluorobenzoic Acid in 1, 4-Dioxane

For the present study, the estimation of the static dielectric constants (0 ), dielectric constant () at an angular frequency and dielectric loss () of methyl, ethyl and propyl amines with 2-fluorobenzoic acid in 1,4-dioxane were carried using Klystron microwave bench at frequency 9.43GHz. Using the dielectric parameters, the overall relaxation time (1 ) and group rotation relaxation time (2 ) of the polar solute molecules and average relaxation times (0 ) were also determined using Higasi and Gopalakrishna method employing Debye’s equations. The obtained results revealed that, out of five different molar ratios, relaxation time () is maximum at 1:1 molar concentration for all the systems due to inter and intramolecular interactions through hydrogen bonding. In addition, the dipole moment, activation viscous flow (f) and dielectric relaxation (f ) due to molar free energy also been discussed.

Properties of Cmc21-X2As2O (X = Si, Ge, and Sn) by First-Principles Calculations

For the compounds Cmc21-X2As2O (X = Si, Ge, and Sn), the stabilities are verified by the elastic constants and the phonon dispersion spectra. The structural, mechanical, electronic, and optical properties are investigated by using density functional theory (DFT) calculations. For Cmc21-X2As2O, the mechanical strengths in the [100], [010], and [001] directions are studied. Young’s modulus for Cmc21-Ge2As2O is more anisotropic than that of Cmc21-Si2As2O and Cmc21-Sn2As2O. The band structures of Cmc21-Si2As2O and Cmc21-Sn2As2O show that they are indirect-bandgap semiconductors with bandgaps of 2.744 and 2.201 eV, by using the HSE06 hybrid functional. Cmc21-Ge2As2O is a direct narrow-bandgap semiconductor with a bandgap of 2.131 eV. The static dielectric constants of Cmc21-Si2As2O and Cmc21-Sn2As2O in the [001] direction are higher than those in the [100] and [010] directions. The static dielectric constant of Cmc21-Ge2As2O in the [001] direction is lower than those in the [100] and [010] directions.

Optical properties and electronic polarizability of boron-antimonide semiconductor

The high-frequency and static dielectric constants, the reflex index, the total optical electronegativity difference, the bulk modulus, the micro-hardness, the plasmon energy and the electronic polarizability of cubic zincblende boron-antimonide semiconductor have been estimated by using some empirical formulas. These parameters are analyzed by comparing them against the available experimental and theoretical data. In general, our obtained results agree well with other theoretical data from the literature.

Quasi-linear correlation between high-frequency and static die-lectric constants in II-VI and III-V semiconductors

A quantitative form of the linear correlation between the high-frequency and static dielectric constants in ANB8-N (N = 2, 3) tetrahedrally coordinated semiconductor materials, and also in I-VII group alkali halides was studied. So, a quasi-linear relationship was found between the high-frequency and the static dielectric constants for some selected II-VI (ZnS, ZnSe, ZnTe and CdTe) and III-V (AlP, AlAs, AlSb,….etc) cubic zincblende type materials, in the other side a weak uphill linear relationship has been found in the case of I-VII (LiF, NaF, LiCl,….etc) group alkali halides compounds. In the case of II-VI and III-V cubic zincblende semiconductors, the linear regression is established with a correlation coefficient ( ) of about 0.98. The significance of the linear regression is given as the probability P <0.0001 of the null hypothesis.

A first-principles study of the effects of different Al constituents on Ga1−xAlxN nanowires

In order to investigate the influences of different Al constituents on Ga[Formula: see text]Al[Formula: see text]N nanowires, the formation energy, stability, band structure, densities of states and optical properties of Ga[Formula: see text]Al[Formula: see text]N nanowires with different Al constituents are calculated using first-principles plane-wave ultrasoft pseudopotential method. Results show that Ga[Formula: see text]Al[Formula: see text]N nanowires become more stable with increasing Al constituent. Bandgap of Ga[Formula: see text]Al[Formula: see text]N nanowires increases as the Al constituent increases but with a lower amplification compared with bulk Ga[Formula: see text]Al[Formula: see text]N. The peaks of static dielectric constants show a decreasing trend and move towards high-energy side as Al constituent increases. The absorption of Ga[Formula: see text]Al[Formula: see text]N nanowires shows an interesting phenomenon that it firstly increases and then decreases slightly as the Al constituent increases. Reflectivity of Ga[Formula: see text]Al[Formula: see text]N nanowires is much smaller than that of the bulk. The optical properties of Ga[Formula: see text]Al[Formula: see text]N nanowires show a blueshift effect as Al composition increases. According to these calculations, it is found that Ga[Formula: see text]Al[Formula: see text]N nanowires are appropriate to be applied into photoelectric detecting materials by adjusting the Al constituent of Ga[Formula: see text]Al[Formula: see text]N nanowires.