Interesting Research
I am interesting in chemical and physical properties of bulk and nano-materials (film, surface and interface) by analyzing the chemical bands and electronic structures of materials using first principle calculations. I am also interesting in topological insulator.
Previous Research
My research focuses on the electronic and physical properties of two-dimensional topological insulators by first principle calculations now. My PhD research focused on topological insulators and transition metal compounds. Utilizing first principle calculations based on density functional theory, I have studied bulk properties of these materials. The results show that chemical bonds and electronic structures affect the crystal, mechanical, optical and magnetic properties of materials.
Firstly, I have calculated several AB2C full-Heusler compounds using GGA+U. The results show full-Heusler compounds with half-filled d orbitals and d5-d5-s2-p6 electronic structures are topological insulators, which will double enlarge the range of topological insulators candidates. The band structures of full-Heusler compounds are affected by the covalent bonding of A-B and B-C jointly. The spin-up and spin-down electrons influence the orbitals and induces the magnetism. All full-Heusler compounds with the magnetic moments about 9 μB are antiferromagnets, which can lead to the image magnetic monopole effect and provide a new design of a tunable optical modulator. [Phys. Rev. B 83, (2011) 235125]
Secondly, we investigate the chemical bonds of binary metallic compounds. Owing to the partly metallic bonding, Phillips model cannot analyze the chemical bonds. By first principle calculations, we have confirmed that the percentage of metallic bonding in multiplex chemical bonds is large for most of these compounds and cannot be ignored. The redefinition Phillips ionicity results in well correspondence for the hardness calculation of transition metal carbides and nitrides. It is confirmed that the s-p-d hybridization in transition metal carbides and nitrides indeed enhances the hardness of materials. [Solid. State. Comm, 150, (2010) 37-38]
Thirdly, I have investigated the dielectric constant of binary semiconductors. I have indicated that the s electrons levels of non-metals have lower transition probability than that of other valence electrons, which leads to the mistake estimation for Levine model. By first principle calculations, we have confirmed that the s electrons levels of non-metals have only half contribution comparing with other valence electrons. Thus, Levine model should be improved, which leads to more accurate prediction on dielectric constants and average optical energy gaps for transition metallic compounds. [J. Appl. Phys, 106, (2009) 094102]
Finally, the structures of a series of fabricated high entropy alloys are examined by experiment and theory. The principle components in the alloys could be divided into two groups by electronegativity and atomic diameter. As result, the high entropy alloys has a B2 structure, not an A2. This is confirmed by the computer simulation and thermodynamics. [J. Appl. Phys, 104, (2008) 113504]
I am interesting in chemical and physical properties of bulk and nano-materials (film, surface and interface) by analyzing the chemical bands and electronic structures of materials using first principle calculations. I am also interesting in topological insulator.
Previous Research
My research focuses on the electronic and physical properties of two-dimensional topological insulators by first principle calculations now. My PhD research focused on topological insulators and transition metal compounds. Utilizing first principle calculations based on density functional theory, I have studied bulk properties of these materials. The results show that chemical bonds and electronic structures affect the crystal, mechanical, optical and magnetic properties of materials.
Firstly, I have calculated several AB2C full-Heusler compounds using GGA+U. The results show full-Heusler compounds with half-filled d orbitals and d5-d5-s2-p6 electronic structures are topological insulators, which will double enlarge the range of topological insulators candidates. The band structures of full-Heusler compounds are affected by the covalent bonding of A-B and B-C jointly. The spin-up and spin-down electrons influence the orbitals and induces the magnetism. All full-Heusler compounds with the magnetic moments about 9 μB are antiferromagnets, which can lead to the image magnetic monopole effect and provide a new design of a tunable optical modulator. [Phys. Rev. B 83, (2011) 235125]
Secondly, we investigate the chemical bonds of binary metallic compounds. Owing to the partly metallic bonding, Phillips model cannot analyze the chemical bonds. By first principle calculations, we have confirmed that the percentage of metallic bonding in multiplex chemical bonds is large for most of these compounds and cannot be ignored. The redefinition Phillips ionicity results in well correspondence for the hardness calculation of transition metal carbides and nitrides. It is confirmed that the s-p-d hybridization in transition metal carbides and nitrides indeed enhances the hardness of materials. [Solid. State. Comm, 150, (2010) 37-38]
Thirdly, I have investigated the dielectric constant of binary semiconductors. I have indicated that the s electrons levels of non-metals have lower transition probability than that of other valence electrons, which leads to the mistake estimation for Levine model. By first principle calculations, we have confirmed that the s electrons levels of non-metals have only half contribution comparing with other valence electrons. Thus, Levine model should be improved, which leads to more accurate prediction on dielectric constants and average optical energy gaps for transition metallic compounds. [J. Appl. Phys, 106, (2009) 094102]
Finally, the structures of a series of fabricated high entropy alloys are examined by experiment and theory. The principle components in the alloys could be divided into two groups by electronegativity and atomic diameter. As result, the high entropy alloys has a B2 structure, not an A2. This is confirmed by the computer simulation and thermodynamics. [J. Appl. Phys, 104, (2008) 113504]