اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA first-principles study of the electronic structure and stability of Be(BH4)2
114
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Alanates and boranates are studied intensively because of their potential use as hydrogen storage materials. In this paper we present a first-principles study of the electronic structure and the energetics of beryllium boranate, Be(BH4)2. From total energy calculations we show that - in contrast to the other boranates and alanates - hydrogen desorption directly to the elements is likely, and is at least competitive with desorption to the elemental hydride (BeH2). The formation enthalpy of Be(BH4)2 is only -0.12 eV/H2 (at T=0K). This low value can be rationalized by the participation of all atoms in the covalent bonding, in contrast to the ionic bonding observed in other boranates. From calculations of thermodynamic properties at finite temperature we estimate a decomposition temperature of 162 K at a pressure of 1 bar.
قيم البحث
اقرأ أيضاً
The molybdate oxides SrMoO$_3$, PbMoO$_3$, and LaMoO$_3$ are a class of metallic perovskites that exhibit interesting properties including high mobility, and unusual resistivity behavior. We use first-principles methods based on density functional th
eory to explore the electronic, crystal, and magnetic structure of these materials. In order to account for the electron correlations in the partially-filled Mo $4d$ shell, a local Hubbard $U$ interaction is included. The value of $U$ is estimated via the constrained random-phase approximation approach, and the dependence of the results on the choice of $U$ are explored. For all materials, GGA+$U$ predicts a metal with an orthorhombic, antiferromagnetic structure. For LaMoO$_3$, the $Pnma$ space group is the most stable, while for SrMoO$_3$ and PbMoO$_3$, the $Imma$ and $Pnma$ structures are close in energy. The $R_4^+$ octahedral rotations for SrMoO$_3$ and PbMoO$_3$ are found to be overestimated compared to the experimental low-temperature structure.
By means of first-principles calculations, the structural stability, mechanical properties and electronic structure of the newly synthesized incompressible Re2C, Re2N, Re3N and an analogous compound Re3C have been investigated. Our results agree well
with the available experimental and theoretical data. The proposed Re3C is shown to be energetically, mechanically and dynamically stable and also incompressible. Furthermore, it is suggested that the incompressibility of these compounds is originated from the strong covalent bonding character with the hybridization of 5d orbital of Re and the 2p orbital of C or N, and a zigzag topology of interconnected bonds, e.g., Re-Re, Re-C or Re-N bonding.
We have studied the electronic structure of CdS/ZnSe coupled quantum dot, a novel heterostructure at the nano-scale. Our calculations reveal CdS/ZnSe coupled quantum dots to be of type-II in nature where the anion-p states play an important role in d
eciding the band offset for the highest occupied molecular orbitals (HOMO). We show that the offsets of HOMO as well as the lowest unoccupied molecular orbitals (LUMO) can be tuned by changing the sizes of the components of the coupled quantum dot, thereby providing an additional control parameter to tune the band gap and the optical properties. Our investigations also suggest that formation of alloy near the interface has very little influence on the band offsets, although it affects the spatial localization of the quantum states from the individual components. Comparing the influence of strain on coupled quantum dots and core/shell nanowires, we find strain practically has no role in the electronic structure of coupled quantum dots as the small effective area of the interface in a coupled quantum dot helps a large part of the structure remain free from any substantial strain. We argue that in contrast to core-shell nanowires, quantum confinement is the key parameter that controls the electronic properties of coupled quantum dot and should therefore be an ideal candidate for the design of a quantum device.
The full-potential linearized augmented plane wave method with the generalized gradient approximation for the exchange-correlation potential (FLAPW-GGA) is used to predict the electronic and elastic properties of the newly discovered superconducting
nanolaminate Ti2InC. The band structure, density of states and Fermi surface features are discussed. The optimized lattice parameters, independent elastic constants, bulk and shear moduli, compressibility are evaluated and discussed. The elastic parameters of the polycrystalline Ti2InC ceramics are estimated numerically for the first time.
We perform a systematic first-principles study of phosphorene in the presence of typical monovalent (hydrogen, fluorine) and divalent (oxygen) impurities. The results of our modeling suggest a decomposition of phosphorene into weakly bonded one-dimen
sional (1D) chains upon single- and double-side hydrogenation and fluorination. In spite of a sizable quasiparticle band gap (2.29 eV), fully hydrogenated phosphorene found to be dynamically unstable. In contrast, full fluorination of phosphorene gives rise to a stable structure, being an indirect gap semiconductor with the band gap of 2.27 eV. We also show that fluorination of phosphorene from the gas phase is significantly more likely than hydrogenation due to the relatively low energy barrier for the dissociative adsorption of F2 (0.19 eV) compared to H2 (2.54 eV). At low concentrations, monovalent impurities tend to form regular atomic rows phosphorene, though such patterns do not seem to be easily achievable due to high migration barriers (1.09 and 2.81 eV for H2 and F2, respectively). Oxidation of phosphorene is shown to be a qualitatively different process. Particularly, we observe instability of phosphorene upon oxidation, leading to the formation of disordered amorphous-like structures at high concentrations of impurities.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
