Zhishuo Huang - Academia.edu (original) (raw)

Papers by Zhishuo Huang

Physical Review B

Compared to isolated C 3− 60 ions, characterized by a three-dimensional equipotential trough at t... more Compared to isolated C 3− 60 ions, characterized by a three-dimensional equipotential trough at the bottom of the lowest adiabatic potential energy surface (APES), the Jahn-Teller (JT) effect in cubic fullerides is additionally influenced by the interaction of JT distortions at C60 sites with vibrational modes of the lattice. This leads to modification of JT stabilization energy and to the warping of the trough at each fullerene site, as well as to the interaction of JT distortions at different sites. Here we investigate these effects in three fcc fullerides with A=K,Rb,Cs and in Cs3C60 with bcc (A15) structure. DFT calculations of orbital vibronic coupling constants at C60 sites and of phonon spectra have been done for fully ordered lattices (1 C60/u.c.). Based on them the elastic response function for local JT distortions has been evaluated and the lowest APES investigated. To this end an expression for the latter in function of trough coordinates of all sites has been derived. The results show that the JT stabilization energy slightly increases compared to an isolated C 3− 60 and a warping of the trough of few meV occurs. The interaction of JT distortions on nearest-and next-nearest-neighbor fullerene sites is of similar order of magnitude. These effects arise first of all due to the interaction of C60 sites with the displacements of neighbor alkali atoms and are more pronounced in fcc fullerides than in the A15 compound. The results of this study support the picture of weakly hindered independent rotations of JT deformations at C60 sites in cubic A3C60.

Physical Review B, 2022

In insulating lanthanides, unquenched orbital momentum and weak crystal-field (CF) splitting of t... more In insulating lanthanides, unquenched orbital momentum and weak crystal-field (CF) splitting of the atomic J multiplet at lanthanide ions result in a highly ranked (multipolar) exchange interaction between them and a complex low-temperature magnetic order not fully uncovered by experiment. Explicitly correlated ab initio methods proved to be highly efficient for an accurate description of CF multiplets and magnetism of individual lanthanide ions in such materials. Here we extend this ab initio methodology and develop a first-principles microscopic theory of multipolar exchange interaction between J-multiplets in f metal compounds. The key point of the approach is a complete account of Goodenough's exchange mechanism along with traditional Anderson's superexchange and other contributions, the former being dominant in many lanthanide materials. Application of this methodology to the description of the ground-state order in the neodymium nitride with rocksalt structure reveals the multipolar nature of its ferromagnetic order. We found that the primary and secondary order parameters (of T1u and Eg symmetry, respectively) contain non-negligible Jtensorial contributions up to the ninth order. The calculated spin-wave dispersion and magnetic and thermodynamic properties show that they cannot be simulated quantitatively by confining to the ground CF multiplet on the Nd sites. Our results demonstrate that the ab initio approach to the low-energy Hamiltonian represents a powerful tool for the study of materials with complex magnetic order.

arXiv: Strongly Correlated Electrons, 2020

Theory of superexchange interaction between JJJ-multiplets in fff metal compounds is developed fo... more Theory of superexchange interaction between JJJ-multiplets in fff metal compounds is developed for an adequate description of Goodenough mechanism induced by the electron transfer between the magnetic fff orbitals and empty ddd and sss orbitals. The developed multipolar exchange model is applied to ferromagnetic NdN by using first principles microscopic parameters. The multipolar interaction parameters up to nineth order are quantitatively determined, and the significance of the higher order interaction is confirmed. The basic magnetic properties such as magnetization and magnetic susceptibility of NdN are well reproduced with the model. In the calculated ferromagnetic phase, it is shown that the quadrupole and octupole moments develop (within ground Gamma_8\Gamma_8Gamma_8 multiplets), unambiguously indicating the significance of the multipolar interactions.

Bulletin of the American Physical Society, 2020

Physical Review Research, 2020

Authorea

Vibronic coupling parameters for C + 60 were derived via DFT calculations with hybrid B3LYP and C... more Vibronic coupling parameters for C + 60 were derived via DFT calculations with hybrid B3LYP and CAM-B3LYP functional, based on which the static Jahn-Teller effect were analyzed. The global minima of adiabatic potential energy surface (APES) shows a D 5d Jahn-Teller deformation, with stabilization energies of 110 and 129 meV (with B3LYP and CAM-B3LYP respectively), which are two times larger than that in C − 60 , suggesting the crucial role of the dynamical Jahn-Teller effect. Present results enable us to assess the actual situation of dynamical Jahn-Teller effect in C + 60 and excited C 60 in combination with the established parameters for C − 60 .

International Journal of Quantum Chemistry, 2019

The Jahn-Teller effect of C 60 anions in the first electronically excited states was theoreticall... more The Jahn-Teller effect of C 60 anions in the first electronically excited states was theoretically investigated. The orbital vibronic coupling parameters for the t 1g next lowest unoccupied molecular orbitals were derived from the Kohn-Sham orbital levels with hybrid B3LYP functional by using the frozen phonon approach. With the use of these coupling parameters, the vibronic states of the first excited C − 60 were derived by exactly diagonalizing the dynamical Jahn-Teller Hamiltonian. The dynamical Jahn-Teller stabilization energy of the first excited C − 60 is stronger than that of the ground electronic states.

Journal of Applied Physics, 2017

Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap se... more Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap sensitively dependent on the number of monolayers combined by the van der Waals interaction according to our calculations based on the density functional theory. It was found that the frontier orbitals of the valence band maximum and the conduction band minimum are mainly contributed by pz and px+y orbitals of Se, which are sensitive to the out-of-plane and the in-plane lattice constants, respectively. The van der Waals force enhances the bonding out-of-plane, which in turn influences the bonding in-plane. We explain that the layer number dependent bandgap has the same electronic reason as the strain dependent bandgap based on the scenario above. This work shows the flexibilities of tuning the electronic and optical properties of PtSe2 in a wide range, which provides an advantage for applications of PtSe2 in sensors.

Nanotechnology, 2016

Monolayer transition-metal dichalcogenides (TMDCs) MX2 (M = Mo, W, Zr, Hf, etc; X = S, Se, Te) ha... more Monolayer transition-metal dichalcogenides (TMDCs) MX2 (M = Mo, W, Zr, Hf, etc; X = S, Se, Te) have become well-known in recent times for their promising applications in thermoelectrics and field effect transistors. In this work, we perform a systematic study on the thermoelectric properties of monolayer ZrSe2 and HfSe2 using first-principles calculations combined with Boltzmann transport equations. Our results point to a competitive thermoelectric figure of merit (close to 1 at optimal doping) in both monolayer ZrSe2 and HfSe2, which is markedly higher than previous explored monolayer TMDCs such as MoS2 and MoSe2. We also reveal that the higher figure of merits arise mainly from their low lattice thermal conductivity, and this is partly due to the strong coupling of acoustic modes with low frequency optical modes. It is found that the figure of merits can be better optimized in n-type than in p-type. In particular, the performance of HfSe2 is superior to ZrSe2 at a higher temperature. Our results suggest that monolayer ZrSe2 and HfSe2 with lower lattice thermal conductivity than usual monolayer TMDCs are promising candidates for thermoelectric applications.

2D Materials, 2016

For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-) nanosheets... more For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-) nanosheets have been grown by chemical vapor deposition. The individual nanosheets are well [001] oriented, with highly crystalline quality. Far different from conventional van der Waals epitaxial growth mechanism for two-dimensional transition metal dichalcogenides, a novel dangling-bond-assisted self-seeding growth mechanism is proposed to describe the growth of V- nanosheets: difficult migration of adatoms on substrate surface results in seeds growing perpendicularly to the substrate; V- nanosheets inherit the growth direction of seeds; V- nanosheets further expand in the in-plane direction with time evolution. Moreover, the V- nanosheets show strong and broadened photons absorption from near infrared to ultraviolet; the V--based photodetector exhibits an ultrafast photoresponse time of 24 ms, and a high photosensitivity ca. 103 for 405 nm laser.

Journal of Alloys and Compounds, 2015

Electronic structures of Rh 2 TMSn (TM = Cr, Mn, Fe, Co, Ni and Cu) full Heusler compounds are ca... more Electronic structures of Rh 2 TMSn (TM = Cr, Mn, Fe, Co, Ni and Cu) full Heusler compounds are calculated by the state-of-the-art electronic structure codes with the local density approximation aiming to understand the structure instability microscopically. The instability of the compounds can be explained by the band Jahn-Teller effect. The compounds can be categorized into two groups: In the first group, the density of states at the Fermi level are contributed mainly from Rh, while in the rest, both the Rh and TM atoms contribute. The high density of states at the Fermi level of the first group compounds may be smoothed and the highly symmetric phase is stable as found in experiments. The compounds in the second group tetragonally distort according to our calculation and was found in the experiments.

Nano Research, 2014

Neither of the two typical two-dimensional materials, graphene and single layer MoS 2 , are good ... more Neither of the two typical two-dimensional materials, graphene and single layer MoS 2 , are good enough for developing semiconductor logical devices. We calculated the electron mobility of 14 two-dimensional semiconductors with composition of MX 2 , where M (=Mo, W, Sn, Hf, Zr and Pt) are transition metals, and Xs are S, Se and Te. We approximated the electron phonon scattering matrix by deformation potentials, within which long wave longitudinal acoustical and optical phonon scatterings were included. Piezoelectric scattering in the compounds without inversion symmetry is also taken into account. We found that out of the 14 compounds, WS 2 , PtS 2 and PtSe 2 are promising for logical devices regarding the possible high electron mobility and finite band gap. Especially, the phonon limited electron mobility in PtSe 2 reaches about 4000 cm 2 •V −1 •s −1 at room temperature, which is the highest among the compounds with an indirect bandgap of about 1.25 eV under the local density approximation. Our results can be the first guide for experiments to synthesize better two-dimensional materials for future semiconductor devices.

Journal of Applied Physics, 2017

Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap se... more Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap sensitively dependent on the number of monolayers combined by the van der Waals interaction according to our calculations based on the density functional theory. It was found that the frontier orbitals of the valence band maximum and the conduction band minimum are mainly contributed by pz and px+y orbitals of Se, which are sensitive to the out-of-plane and the in-plane lattice constants, respectively. The van der Waals force enhances the bonding out-of-plane, which in turn influences the bonding in-plane. We explain that the layer number dependent bandgap has the same electronic reason as the strain dependent bandgap based on the scenario above. This work shows the flexibilities of tuning the electronic and optical properties of PtSe2 in a wide range, which provides an advantage for applications of PtSe2 in sensors.

Physical Review B

Compared to isolated C 3− 60 ions, characterized by a three-dimensional equipotential trough at t... more Compared to isolated C 3− 60 ions, characterized by a three-dimensional equipotential trough at the bottom of the lowest adiabatic potential energy surface (APES), the Jahn-Teller (JT) effect in cubic fullerides is additionally influenced by the interaction of JT distortions at C60 sites with vibrational modes of the lattice. This leads to modification of JT stabilization energy and to the warping of the trough at each fullerene site, as well as to the interaction of JT distortions at different sites. Here we investigate these effects in three fcc fullerides with A=K,Rb,Cs and in Cs3C60 with bcc (A15) structure. DFT calculations of orbital vibronic coupling constants at C60 sites and of phonon spectra have been done for fully ordered lattices (1 C60/u.c.). Based on them the elastic response function for local JT distortions has been evaluated and the lowest APES investigated. To this end an expression for the latter in function of trough coordinates of all sites has been derived. The results show that the JT stabilization energy slightly increases compared to an isolated C 3− 60 and a warping of the trough of few meV occurs. The interaction of JT distortions on nearest-and next-nearest-neighbor fullerene sites is of similar order of magnitude. These effects arise first of all due to the interaction of C60 sites with the displacements of neighbor alkali atoms and are more pronounced in fcc fullerides than in the A15 compound. The results of this study support the picture of weakly hindered independent rotations of JT deformations at C60 sites in cubic A3C60.

Physical Review B, 2022

In insulating lanthanides, unquenched orbital momentum and weak crystal-field (CF) splitting of t... more In insulating lanthanides, unquenched orbital momentum and weak crystal-field (CF) splitting of the atomic J multiplet at lanthanide ions result in a highly ranked (multipolar) exchange interaction between them and a complex low-temperature magnetic order not fully uncovered by experiment. Explicitly correlated ab initio methods proved to be highly efficient for an accurate description of CF multiplets and magnetism of individual lanthanide ions in such materials. Here we extend this ab initio methodology and develop a first-principles microscopic theory of multipolar exchange interaction between J-multiplets in f metal compounds. The key point of the approach is a complete account of Goodenough's exchange mechanism along with traditional Anderson's superexchange and other contributions, the former being dominant in many lanthanide materials. Application of this methodology to the description of the ground-state order in the neodymium nitride with rocksalt structure reveals the multipolar nature of its ferromagnetic order. We found that the primary and secondary order parameters (of T1u and Eg symmetry, respectively) contain non-negligible Jtensorial contributions up to the ninth order. The calculated spin-wave dispersion and magnetic and thermodynamic properties show that they cannot be simulated quantitatively by confining to the ground CF multiplet on the Nd sites. Our results demonstrate that the ab initio approach to the low-energy Hamiltonian represents a powerful tool for the study of materials with complex magnetic order.

arXiv: Strongly Correlated Electrons, 2020

Theory of superexchange interaction between JJJ-multiplets in fff metal compounds is developed fo... more Theory of superexchange interaction between JJJ-multiplets in fff metal compounds is developed for an adequate description of Goodenough mechanism induced by the electron transfer between the magnetic fff orbitals and empty ddd and sss orbitals. The developed multipolar exchange model is applied to ferromagnetic NdN by using first principles microscopic parameters. The multipolar interaction parameters up to nineth order are quantitatively determined, and the significance of the higher order interaction is confirmed. The basic magnetic properties such as magnetization and magnetic susceptibility of NdN are well reproduced with the model. In the calculated ferromagnetic phase, it is shown that the quadrupole and octupole moments develop (within ground Gamma_8\Gamma_8Gamma_8 multiplets), unambiguously indicating the significance of the multipolar interactions.

Bulletin of the American Physical Society, 2020

Physical Review Research, 2020

Authorea

Vibronic coupling parameters for C + 60 were derived via DFT calculations with hybrid B3LYP and C... more Vibronic coupling parameters for C + 60 were derived via DFT calculations with hybrid B3LYP and CAM-B3LYP functional, based on which the static Jahn-Teller effect were analyzed. The global minima of adiabatic potential energy surface (APES) shows a D 5d Jahn-Teller deformation, with stabilization energies of 110 and 129 meV (with B3LYP and CAM-B3LYP respectively), which are two times larger than that in C − 60 , suggesting the crucial role of the dynamical Jahn-Teller effect. Present results enable us to assess the actual situation of dynamical Jahn-Teller effect in C + 60 and excited C 60 in combination with the established parameters for C − 60 .

International Journal of Quantum Chemistry, 2019

The Jahn-Teller effect of C 60 anions in the first electronically excited states was theoreticall... more The Jahn-Teller effect of C 60 anions in the first electronically excited states was theoretically investigated. The orbital vibronic coupling parameters for the t 1g next lowest unoccupied molecular orbitals were derived from the Kohn-Sham orbital levels with hybrid B3LYP functional by using the frozen phonon approach. With the use of these coupling parameters, the vibronic states of the first excited C − 60 were derived by exactly diagonalizing the dynamical Jahn-Teller Hamiltonian. The dynamical Jahn-Teller stabilization energy of the first excited C − 60 is stronger than that of the ground electronic states.

Journal of Applied Physics, 2017

Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap se... more Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap sensitively dependent on the number of monolayers combined by the van der Waals interaction according to our calculations based on the density functional theory. It was found that the frontier orbitals of the valence band maximum and the conduction band minimum are mainly contributed by pz and px+y orbitals of Se, which are sensitive to the out-of-plane and the in-plane lattice constants, respectively. The van der Waals force enhances the bonding out-of-plane, which in turn influences the bonding in-plane. We explain that the layer number dependent bandgap has the same electronic reason as the strain dependent bandgap based on the scenario above. This work shows the flexibilities of tuning the electronic and optical properties of PtSe2 in a wide range, which provides an advantage for applications of PtSe2 in sensors.

Nanotechnology, 2016

Monolayer transition-metal dichalcogenides (TMDCs) MX2 (M = Mo, W, Zr, Hf, etc; X = S, Se, Te) ha... more Monolayer transition-metal dichalcogenides (TMDCs) MX2 (M = Mo, W, Zr, Hf, etc; X = S, Se, Te) have become well-known in recent times for their promising applications in thermoelectrics and field effect transistors. In this work, we perform a systematic study on the thermoelectric properties of monolayer ZrSe2 and HfSe2 using first-principles calculations combined with Boltzmann transport equations. Our results point to a competitive thermoelectric figure of merit (close to 1 at optimal doping) in both monolayer ZrSe2 and HfSe2, which is markedly higher than previous explored monolayer TMDCs such as MoS2 and MoSe2. We also reveal that the higher figure of merits arise mainly from their low lattice thermal conductivity, and this is partly due to the strong coupling of acoustic modes with low frequency optical modes. It is found that the figure of merits can be better optimized in n-type than in p-type. In particular, the performance of HfSe2 is superior to ZrSe2 at a higher temperature. Our results suggest that monolayer ZrSe2 and HfSe2 with lower lattice thermal conductivity than usual monolayer TMDCs are promising candidates for thermoelectric applications.

2D Materials, 2016

For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-) nanosheets... more For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-) nanosheets have been grown by chemical vapor deposition. The individual nanosheets are well [001] oriented, with highly crystalline quality. Far different from conventional van der Waals epitaxial growth mechanism for two-dimensional transition metal dichalcogenides, a novel dangling-bond-assisted self-seeding growth mechanism is proposed to describe the growth of V- nanosheets: difficult migration of adatoms on substrate surface results in seeds growing perpendicularly to the substrate; V- nanosheets inherit the growth direction of seeds; V- nanosheets further expand in the in-plane direction with time evolution. Moreover, the V- nanosheets show strong and broadened photons absorption from near infrared to ultraviolet; the V--based photodetector exhibits an ultrafast photoresponse time of 24 ms, and a high photosensitivity ca. 103 for 405 nm laser.

Journal of Alloys and Compounds, 2015

Electronic structures of Rh 2 TMSn (TM = Cr, Mn, Fe, Co, Ni and Cu) full Heusler compounds are ca... more Electronic structures of Rh 2 TMSn (TM = Cr, Mn, Fe, Co, Ni and Cu) full Heusler compounds are calculated by the state-of-the-art electronic structure codes with the local density approximation aiming to understand the structure instability microscopically. The instability of the compounds can be explained by the band Jahn-Teller effect. The compounds can be categorized into two groups: In the first group, the density of states at the Fermi level are contributed mainly from Rh, while in the rest, both the Rh and TM atoms contribute. The high density of states at the Fermi level of the first group compounds may be smoothed and the highly symmetric phase is stable as found in experiments. The compounds in the second group tetragonally distort according to our calculation and was found in the experiments.

Nano Research, 2014

Neither of the two typical two-dimensional materials, graphene and single layer MoS 2 , are good ... more Neither of the two typical two-dimensional materials, graphene and single layer MoS 2 , are good enough for developing semiconductor logical devices. We calculated the electron mobility of 14 two-dimensional semiconductors with composition of MX 2 , where M (=Mo, W, Sn, Hf, Zr and Pt) are transition metals, and Xs are S, Se and Te. We approximated the electron phonon scattering matrix by deformation potentials, within which long wave longitudinal acoustical and optical phonon scatterings were included. Piezoelectric scattering in the compounds without inversion symmetry is also taken into account. We found that out of the 14 compounds, WS 2 , PtS 2 and PtSe 2 are promising for logical devices regarding the possible high electron mobility and finite band gap. Especially, the phonon limited electron mobility in PtSe 2 reaches about 4000 cm 2 •V −1 •s −1 at room temperature, which is the highest among the compounds with an indirect bandgap of about 1.25 eV under the local density approximation. Our results can be the first guide for experiments to synthesize better two-dimensional materials for future semiconductor devices.

Journal of Applied Physics, 2017

Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap se... more Besides its promising high electron mobilities at room temperature, PtSe2 has a finite bandgap sensitively dependent on the number of monolayers combined by the van der Waals interaction according to our calculations based on the density functional theory. It was found that the frontier orbitals of the valence band maximum and the conduction band minimum are mainly contributed by pz and px+y orbitals of Se, which are sensitive to the out-of-plane and the in-plane lattice constants, respectively. The van der Waals force enhances the bonding out-of-plane, which in turn influences the bonding in-plane. We explain that the layer number dependent bandgap has the same electronic reason as the strain dependent bandgap based on the scenario above. This work shows the flexibilities of tuning the electronic and optical properties of PtSe2 in a wide range, which provides an advantage for applications of PtSe2 in sensors.