Analysis on the energetics, magnetism and electronic properties in a 45° ZnO grain boundary doped with Gd

Abstract

The structural stability and magnetic properties of a grain boundary (GB) formed by aligning two ZnO single crystals oriented at an angle of 45 is investigated by density functional theory, using generalized gradient approximation (GGA) and taking the U parameter into consideration for the 4f impurity states. We found that the GB is stable with no dangling bonds and inter-granular structures. The stability of defects such as Gd substituted to the Zn site (Gd Zn ), Zn vacancy (V Zn ) and O vacancy (V O ) as well as defect complexes Gd Zn -Gd Zn , Gd Zn -V Zn , and Gd Zn -V O are analyzed using formation energy calculations. It is found that Gd Zn -Gd Zn clusters prefers to form at the GB. The spin polarization at the Gd Zn sites is too localized and the exchange coupling energy is insufficient to overcome the thermal fluctuations. However, we show that the presence of V Zn increases the hybridization between p orbitals of O as well as d orbitals of Zn, which can assist in increasing the magnetic polarization of the system. This work advances the understanding of the ferromagnetism in Gd-doped ZnO, indicating that Gd clustering at the GB is not likely to contribute to the ferromagnetism.

Embrittlement Analysis of $$\sum {{{{5}\left[ {{21}0} \right]} \mathord{\left/ {\vphantom {{{5}\left[ {{21}0} \right]} {\left( {\overline{1}\overline{2}0} \right)}}} \right. \kern-\nulldelimiterspace} {\left( {-{1}-{2}0} \right)}}}$$ FeAl Grain Boundary in Presence of Defects: An Ab Initio Study

“…Such ring patterns have been reported to form in supercells containing grain boundaries. [13][14][15]26,27] The Fe-Al bond length in the pristine GB is 2.48 A ˚, and in the relaxed structure, the bonds are readjusted such that Fe-Al distances vary from 2.3 to 2.6 A ˚. To study the probability of formation of native defects, vacancies are created at the GB by removing one Fe/Al atom at a time such that two different vacancy positions are created for both Fe and Al.…”

“…[11] Interfaces and GBs provide such available sites so that hydrogen can accumulate there, and extant research has shown that the presence of GBs in materials can significantly alter the properties and generate new physical phenomena. [12][13][14][15] Once hydrogen has accumulated at the FeAl GBs, it may reduce the cohesiveness of atoms leading to bond rupture and brittle fracture. [12] Attempts to enhance the ductility of the FeAl alloys have been made and include the formation of a protective oxide layer as well as introduction of ductility-enhancing elements such as Cr, B or C. [11] Vacancies are considered the simplest type of lattice defects, and GBs are the most common planar defects.…”

The conduction process of grain and grain boundary in the semiconductive zirconium oxynitride thin film

“…This process can be employed to analyze the temperature sensitivity and hopping type behaviors of grain and grain boundary in thermistors by analyzing their AC impedance spectroscopies at different temperatures [29]. Furthermore, researchers have confirmed that the appearance of grain boundary can change magnetic and electronic properties of semiconductors [30,31]. According to these different behaviors of grain and grain boundary, their characterizations can be strengthen and applied by changing their component proportion to meet the requirement of different applications.…”