Accurate electrical and spectroscopic properties ofX 1Σ+ BeO from coupled-cluster methods

Summary This paper reports a series of coupled-cluster (CC) calculations through CCSDT on the theoretically challenging ground state of the BeO molecule. Along with CC methods, quadratic configuration interaction (QCI) approximations to CC theory have been used (QCISD and QCISD(T)), which show several dramatic failings. Equilibrium electrical properties (, _xx , and _zz ) and basic spectroscopic properties (r _e, _e,D _e, and infrared intensity (I)) have been computed. Basis set and electron correlation effects are analyzed in order to arrive at accurate values of the dipole moment and polarizability, which are not known experimentally. For the dipole moment, we obtain a value of 6.25 D, with an uncertainty of about 0.1 D. For _xx and _zz , we suggest respective values of 32 and 36 atomic units (a.u.) and error bars of about 1 and 2 a.u. With extended basis sets, the spectroscopic propertiesr _e, _e, andD _e are reproduced to high accuracy, which is the first time this has been achieved for this species byab initio methods. At the highest calculation levels,I is predicted to be very small. AlthoughI has not been measured, some support for this prediction comes from a recent infrared study of BeO-rare gas complexes. The QCI methods are shown to be much more sensitive to basis set, and even with large basis sets yield values of _zz andI which differ from CC results by an order of magnitude and three orders of magnitude, respectively. These differences doubtless arise from the importance of single excitations (T ₁) for this molecule, as several terms involvingT ₁ are neglected in the QCISD approximation compared with CCSD. We also report CC calculations with Brueckner orbitals, which yield results similar to those obtained with restricted Hartree-Fock orbitals.     

ICP-AES法测定矿石中的BeO

报道了采用ICP－AES法测定矿石中的BeO。对试样的溶解进行了选择；考察了其体和无机酸对测定的影响。采用基体匹配法进行测定。在优化条件下，对三个试样进行测定，其相对标准偏差（n=9）为0.28%；回收率为97％－103％。     

Theoretical determination of the differential polarizability and anisotropy of alkaline earth oxide nanoclusters (BeO)n [n = 2–9]: The basis set and electron correlation effects

As an important lineage of metal oxides, alkaline earth oxides have attracted significant interest due to their unique properties and potential applications in material science and industry. In this article, we present the first ab initio (HF, MP2, and CCSD(T)) and density functional theory (TPSSh functional) investigation on the optical properties such as polarizabilities per atom (PPA), differential polarizability per unit (DPPU), and anisotropies of (BeO)_n [n = 2–9] nanoclusters as an illustrative example of alkaline earth oxides nanostructures. Basis set augmentation effects on the studied properties of BeO nanoclusters have been explored by using basis sets of triple‐zeta quality starting from 6‐311G with increasing completeness of the diffuse and polarization functions to the 6‐311+G(3df) basis. Checking carefully the basis set effects, it is shown that the 6‐311+G(3d) basis set provides the best compromise between the accuracy and computational cost. We found a decreasing trend for PPA values of BeO nanoclusters using all considered methods, indicating the strong electron delocalization with increasing cluster size. Moreover, in accordance with the energetic analysis of stability of BeO nanoclusters, the values of PPA show that the (BeO)₄ and (BeO)₆ clusters are the most stable magic numbers compared to the neighbors, satisfying the minimum polarizability principle. The computed values of DPPU demonstrate a strong binding effect in BeO nanoclusters. Taking into account the electron correlation correction (ECC), it is observed that the variations of ECC on dipole polarizabilities are almost smooth for clusters under study. © 2013 Wiley Periodicals, Inc.     

BeO高压相变和声子谱的第一性原理计算

采用第一性原理方法计算了BeO在零温时的高压相变和三种结构在零温零压时的声子谱.相变的计算表明,在122GPa左右的压力下BeO会发生从纤锌矿(B4)结构到氯化钠(B1)结构的相变,而闪锌矿(B3)结构在零温零压下是一种可能的亚稳态结构.采用冷声子方法计算了这三种结构的BeO在零温零压下的声子谱.计算结果表明:B1结构在零温零压下是一种不稳定的结构;尽管B4结构和B3结构具有明显的相似性,仍然可以通过声子谱来很好的区分.最后根据准简谐近似理论计算得到了BeO的高温高压相图.     

Theoretical investigations of the EPR parameters and local structure for Cu2+ in BeO

The electron paramagnetic resonance (EPR) parameters (the anisotropic g factors, the hyperfine structure parameters and the quadrupole coupling constant Q) and local structure for Cu²⁺ in BeO are theoretically investigated from the perturbation formulas of these parameters for a 3d⁹ ion under trigonally distorted tetrahedra. The ligand orbital and spin-orbit coupling contributions are included in the basis of the cluster approach, in view of the strong covalency of the [CuO₄]^6? cluster. From the calculations, the impurity Cu²⁺ is suggested not to occupy exactly the ideal Be²⁺ site but to suffer a slight inward displacement (≈0.024 Å) toward the ligand triangle along the C₃ axis. The theoretical EPR parameters show good agreement with the experimental data.     

Thermoluminescence and low-temperature luminescence of beryllium oxide

Beryllium oxide in the forms of either single crystals (pristine, additively-colored) or hot-pressed ceramic samples was studied in the energy range of 1.2–6.2 eV using both the thermoluminescence (TL) and steady-state X-ray induced luminescence (XRL) techniques. The XRL emission spectra were recorded at 6 and 293 K, whereas TL glow curves were studied after X-ray exposure at T₀ = 6 K upon linear heating in the temperature range from 6 to 293 K. A search for TL manifestations of shallow trapping centers was carried out using a sensitive channel for TL registration in the range of more than six decades of change in intensity. The participation of shallow trapping centers in the process of recombination luminescence excitation at 6–293 K; branching electronic excitations between different recombination channels; the dominance of the self-trapped exciton and F-center emissions in spectra of the low-temperature recombination luminescence in BeO at 6–293 K were discussed.     

Beryllium oxide (BeO) nanotube provides excellent surface towards adenine adsorption: A dispersion-corrected DFT study in gas and water phases

Zigzag (5, 0) BeO nanotube (BeONT) has been examined in detail towards adsorption properties of adenine nucleobase on its surface via D2-DFT calculation method in the gas and water phases. A detailed surface study reveals that there are four orientations for nucleobase adsorption that none of the vibrational spectrums demonstrated imaginary frequency, recognizing that all of the relaxed structures are at the minimum of energy. The minimum and maximum adsorption energies are both in chemisorption regime with calculated values of −140 (−118 BSSE corrected) and −191 (−168 BSSE corrected) in the gas phase, and −181 and −310 kJ/mol in the water phase, using meta-hybrid functional (ꞷB97XD) and 6-31G** basis set. For all positions, BeONT showed p-type semiconducting property because of receiving electronic charge from adenine molecule. Our findings suggest that BeONT could be used as a possible strong carrier for adenine molecule in practical applications.     

Electronic structure of fluorinated and hydrogenated beryllium monoxide nanostructures

Using first‐principles calculations, we investigate the chemical functionalizations of beryllium monoxide (BeO) nanostructures by the fluorine and hydrogen atoms. We find that the hydrogenation weakens the Be–O bonds and causes the instability of semihydrogenated nanosheets, while the fluorination is energetically favorable and forms a stable semifluorinated conformation. More importantly, the semifluorinated BeO sheet exhibits an intrinsic half‐metallic behavior, which is robust with a large half‐metal gap and a high Curie temperature above room temperature. By the same strategy of fluorination, the half‐metallicity can also be achieved in the one‐dimensional BeO nanotubes and nanoribbons. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dipole defects in BeO

Thermally Stimulated Depolarization Currents (TSDC) technique was applied to study the effects of thermal treatments and gamma irradiation in the formation, aggregation and destruction processes of dipole defects in beryllium oxide (BeO). In this work, a TSDC dipole peak was observed at 350 K that was assigned to impurity-vacancy complexes. The TSDC peak presents a linear dependence with the Polarization Voltage (V_P), typical behaviour of defects with dipole origin. Thermal treatments of 1 h were performed between 400 and 900 °C and a decay in the peak intensity was observed. After the gamma irradiation of the thermal treated samples a restoration tendency of the TSDC peak was observed.     

TL, OSL and ESR studies on beryllium oxide

Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermoluminescence (TL) and optically stimulated luminescence (OSL) processes in BeO phosphor. Two defect centres were identified in irradiated BeO phosphor by ESR measurements, which were carried out at room temperature and these were assigned to an O⁻ ion and Al²⁺ centre. The O⁻ ion (hole centre) correlates with the main 190 °C TL peak. The Al²⁺ centre (electron centre), which acts as a recombination centre, also correlates to the 190 °C TL peak. A third centre, observed during thermal annealing studies, is assigned to an O⁻ ion and is related to the high temperature TL at 317 °C. This centre also appears to be responsible for the observed OSL process in BeO phosphor.