Download or read book First principles Study of the Structural Electronic and Magnetic Properties of Double Perovskite Sr2FeReO6 Containing Various Imperfections Project Supported by the National Natural Science Foundation of China Grant No 51501017 written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book First Principles Study of Electronic and Magnetic Structures in Double Perovskites written by Molly Ball and published by . This book was released on 2017 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: At present, electronic devices are reaching their storage and processing limit causing a major push to find materials that can be used in the next generation of devices. Double perovskites with A2BB'O6 stoichiometry form one of the leading classes of materials currently being studied as a potential candidate because of their extremely wide range and tunability of functional properties, along with economic and highly scalable synthesis routes. Having a thorough understanding of their electronic and magnetic structure and their dependence on composition and local structure is the basis for targeted development of novel and optimized double perovskites. While the body of knowledge and rules within the field of materials chemistry has enabled many previous discoveries, recent developments within density functional theory (DFT) allow by now a rather realistic description of the electronic and magnetic properties of materials and especially identification of their origin from geometry and orbital structure. This thesis details computational work based on DFT within several collaborative studies to better understand the electronic and magnetic properties of double perovskites and related materials that show promise for future use in multifunctional devices. First, we will begin with a general introduction to the double perovskite structure, their properties, and the computational methods used to study them. In the next section, we will look at the case of the antiferromagnetic, insulating double perovskite Sr2CoOsO6, where measurements showed that the transition metal ions in the two sublattices undergo magnetic ordering independently of each other, indicating weak magnetic short-range coupling and a dominance of longer-range interactions, which has previously not been observed. Here, we performed DFT calculations to extract the exchange strengths between the ions and explain this unique dominance of the long-range interactions. Then, we will look at studies done on thin films of Sr2CrReO6, where our experimental collaborators found extraordinarily large anisotropy fields and record-breaking strain-tunable magnetocrystalline anisotropy (MCA). We employed first principles calculations that examine the dependence of MCA on strain and could identify orbital magnetism on the Re atoms as the origin of this unique phenomenon. In the last section, we introduce double perovskites as novel lead-free halide solar cell materials, with current focus on Cs2AgBiBr6 and Cs2AgBiCl6. While organic Pb based halides that can be synthesized without expensive clean rooms have achieved within record time efficiencies that rival that of traditional semiconductor based materials, creating quite a buzz within the field of photovoltaics, their Pb content and lacking air stability represented severe roadblocks towards market introduction. Here, we show with band structure calculations that spin-orbit coupling is a much more dominant interaction than in traditional semiconductors and thus needs to be considered when designing novel materials for maximum efficiency. The results of this study have given momentum to investigate additional halides double perovskites. Finally, we will summarize and discuss the importance of computational modeling in order to explore the wide and to date little explored composition space of double perovskites, one of the currently most promising materials classes for novel devices with unique and extremely tunable properties.
Download or read book First principles Hybrid Functional Study of the Electronic Structure and Charge Carrier Mobility in Perovskite CH3NH3SnI3 Project Supported by the National Natural Science Foundation of China Grant No 51172067 the Hunan Provincial Natural Science Fund for Distinguished Young Scholars China Grant No 13JJ1013 the Specialized Research Fund for the Doctoral Program of Higher Education China Grant No 20130161110036 and the New Century Excellent Talents in University China Grant No NCET 12 0171 D written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: We calculate the electronic properties and carrier mobility of perovskite CH3 NH3 SnI3 as a solar cell absorber by using the hybrid functional method. The calculated result shows that the electron and hole mobilities have anisotropies with a large magnitude of 1.4 × 10 4 cm 2 ·V −1 ·s −1 along the y direction. In view of the huge difference between hole and electron mobilities, the perovskite CH3 NH3 SnI3 can be considered as a p-type semiconductor. We also discover a relationship between the effective mass anisotropy and electronic occupation anisotropy. The above results can provide reliable guidance for its experimental applications in electronics and optoelectronics.
Download or read book Effect of Quench Treatment on Fe Mo Order and Magnetic Properties of Double Perovskite Sr2FeMoO6 Supported by the National Natural Science Foundation of China Under Grant No U1304110 and the Doctoral Science Foundation of Henan Normal University Under Grant written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book First Principles Study of Two Dimensional Electron Gas in Perovskite Oxide Heterostructures written by Jianli Cheng and published by . This book was released on 2018 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional electron gas (2DEG) formed at the interface between two insulating perovskite oxides has provided a versatile playground to explore emergent interfacial electronic and magnetic properties. In this thesis our efforts centered on studying the electronic and structural properties of different 2DEG heterostructures (HS), with the goal of designing novel 2DEG HS using first-principles methods. In the first project we studied the [delta]-doping effects on the electronic and energetic properties of LaAlO3/SrTiO3 HS with 23 transition-metal (TM) dopants. It has been found that there is a trade-off between achieving small electron effective mass and obtaining an energetically favorable TM-doped LaAlO3/SrTiO3 system. More importantly, in addition to the experimentally confirmed Mn dopant, we proposed that Fe, Co, Ni, Ru, Rh, Pd, Os and Ir elements can also be promising dopants to yield light effective mass bands and good energetic stability. In the second project we compared the electronic and energetic properties of TiO2/LaAlO3 and LaAlO3/TiO2 HS. We found that TiO2/LaAlO3 is intrinsically metallic and has a larger interfacial charge carrier density, smaller electron effective mass and a stronger interface cohesion than LaAlO3/TiO2, which shows an insulator-to-metal transition at 4 unit cells of LaAlO3. In the third project we introduced a hitherto unknown 2DEG formed at the interface between spinel MgAl2O4 and SrTiO3. Our integrated approach combining experimental measurements and first-principles calculations reveals that an atomic-thin interfacial Ti-Al-O layer with a thickness of about 4Å is key to the observed metallic transport. The 2DEG observed at spinel/perovskite interface implies the existence of emergent phenomena at the interfaces between spinel group minerals and perovskite oxides. In the fourth and fifth project we explored the possibility of creating 2DEG in nonpo- lar/nonpolar perovskite oxide HS. We found that the lattice-mismatch-induced compression strain from the substrate leads to a large polarization in the film, which then drives the charge transfer from the film to the substrate and results in a 2DEG at the interface. In addition, by using high-throughput first-principles calculations and a group of combinatory descriptors, we rapidly designed more than 300 novel nonpolar/nonpolar 2DEG HS. In the final project we introduced Grain Boundary Maker (GBMaker), an efficient and open-source Python library for generating atomic coordinates in periodic grain boundary models. It is designed to construct various grain boundary structures from cubic and non-cubic initial configurations. GBMaker is expected to greatly accelerate the theoretical investigation of grain boundary properties and facilitate the experimental analysis of grain boundary structures as well.
