We present an <em>ab-initio</em>, self-consistent density functional theory (DFT) description of ground state electronic and related properties of hexagonal boron nitride (h-BN). We used a local density ap...We present an <em>ab-initio</em>, self-consistent density functional theory (DFT) description of ground state electronic and related properties of hexagonal boron nitride (h-BN). We used a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) formalism. We rigorously implemented the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). The method ensures a generalized minimization of the energy that is far beyond what can be obtained with self-consistency iterations using a single basis set. The method leads to the ground state of the material, in a verifiable manner, without employing over-complete basis sets. We report the ground state band structure, band gap, total and partial densities of states, and electron and hole effective masses of hexagonal boron nitride (h-BN). Our calculated, indirect band gap of 4.37 eV, obtained with room temperature experimental lattice constants of <em>a</em> = 2.504 <span style="white-space:nowrap;">Å</span> and <em>c </em>= 6.661 <span style="white-space:nowrap;">Å</span>, is in agreement with the measured value of 4.3 eV. The valence band maximum is slightly to the left of the K point, while the conduction band minimum is at the M point. Our calculated, total width of the valence and total and partial densities of states are in agreement with corresponding, experimental findings.展开更多
To search for an alternative for Nd_(2)Fe_(14)B,we have studied the electronic structures of R_(2)M_(14)B compounds,where R stands for rare-earth element and M for Mn,Fe,Co and Ni.By density functional theory(DFT),we ...To search for an alternative for Nd_(2)Fe_(14)B,we have studied the electronic structures of R_(2)M_(14)B compounds,where R stands for rare-earth element and M for Mn,Fe,Co and Ni.By density functional theory(DFT),we discuss the atomic coordination environment and partial density of states(PDOS)in detail,with the emphasis on the interaction between the six kinds of M sites and the R atoms.We systemically calculated the electronic structures of sixty R_(2)M_(14)B compounds to provide systematic and reliable results for explaining the origination of magnetism,which is important for further development of Nd_(2)Fe_(14)B based magnet materials.展开更多
Nonlinear optical(NLO)crystals can be employed to expand the laser frequency and thus are of technical importance in advanced laser science.Noncentrosymmetric rare earth compounds keep attracting broad interest as a s...Nonlinear optical(NLO)crystals can be employed to expand the laser frequency and thus are of technical importance in advanced laser science.Noncentrosymmetric rare earth compounds keep attracting broad interest as a significant branch of NLO materials because the highly distorted structural motifs centered by rare earth ions could remarkably benefit the second harmonic generation.In this review,we proceed from structure-properties relationship and reveal the role of rare earth element in the optical properties of NLO materials.We believe that this work can deepen the understanding of rare earth-based NLO materials and provide some enlightenment for exploring novel practical NLO crystals.展开更多
文摘We present an <em>ab-initio</em>, self-consistent density functional theory (DFT) description of ground state electronic and related properties of hexagonal boron nitride (h-BN). We used a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) formalism. We rigorously implemented the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). The method ensures a generalized minimization of the energy that is far beyond what can be obtained with self-consistency iterations using a single basis set. The method leads to the ground state of the material, in a verifiable manner, without employing over-complete basis sets. We report the ground state band structure, band gap, total and partial densities of states, and electron and hole effective masses of hexagonal boron nitride (h-BN). Our calculated, indirect band gap of 4.37 eV, obtained with room temperature experimental lattice constants of <em>a</em> = 2.504 <span style="white-space:nowrap;">Å</span> and <em>c </em>= 6.661 <span style="white-space:nowrap;">Å</span>, is in agreement with the measured value of 4.3 eV. The valence band maximum is slightly to the left of the K point, while the conduction band minimum is at the M point. Our calculated, total width of the valence and total and partial densities of states are in agreement with corresponding, experimental findings.
基金Youth fund of the national natural science foundation of China(Project Numbers:51104078)Yunnan applied basic researchproject(Project Numbers:2011FA008and 2013FZ012)
基金supported by the National Natural Science Foundation of China(No.21703248)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB20000000)the STS program under cooperative agreement between Fujian Province and Chinese Academy of Sciences(No.2017T3004)。
文摘To search for an alternative for Nd_(2)Fe_(14)B,we have studied the electronic structures of R_(2)M_(14)B compounds,where R stands for rare-earth element and M for Mn,Fe,Co and Ni.By density functional theory(DFT),we discuss the atomic coordination environment and partial density of states(PDOS)in detail,with the emphasis on the interaction between the six kinds of M sites and the R atoms.We systemically calculated the electronic structures of sixty R_(2)M_(14)B compounds to provide systematic and reliable results for explaining the origination of magnetism,which is important for further development of Nd_(2)Fe_(14)B based magnet materials.
基金Project supported by the National Natural Science Foundation of China(51972208,51832007)。
文摘Nonlinear optical(NLO)crystals can be employed to expand the laser frequency and thus are of technical importance in advanced laser science.Noncentrosymmetric rare earth compounds keep attracting broad interest as a significant branch of NLO materials because the highly distorted structural motifs centered by rare earth ions could remarkably benefit the second harmonic generation.In this review,we proceed from structure-properties relationship and reveal the role of rare earth element in the optical properties of NLO materials.We believe that this work can deepen the understanding of rare earth-based NLO materials and provide some enlightenment for exploring novel practical NLO crystals.
