Yan-ling Li | Jiangsu Normal University (original) (raw)
Papers by Yan-ling Li
The structural, dynamical, and electronic properties of compressed SrC 2 were systematically inve... more The structural, dynamical, and electronic properties of compressed SrC 2 were systematically investigated up to 200 GPa by using ab initio method. Three new phases are obtained by means of evolutionary algorithm. The confirmed most stable structure has C2/c symmetry at zero pressure, which transforms into an orthorhombic Cmcm phase at 4.5 GPa, followed by another orthorhombic Immm phase, which is stabilized at wide pressure range of 21.5-123.5 GPa, and then transformed into MgB 2 -type phase (space group, P6/mmm). Although SrC 2 has similar structural transformation to that of compressed CaC 2 , SrC 2 holds small electron-phonon coupling, which leads to its low superconducting critical temperature (only 1.8 K).
The structural, elastic and electronic properties of ReN are investigated by first-principles cal... more The structural, elastic and electronic properties of ReN are investigated by first-principles calculations based on density functional theory (DFT). The most stable structure of ReN is a NiAs-like structure, belonging to space group P6 3 /mmc with a = 2.7472 and c = 5.8180 Å. ReN is a metallic ultraincompressible solid and it exhibits low elastic anisotropy. Its linear incompressibility along the c-axis exceeds that of diamond. Its ultra-incompressibility is attributed to the high valence electron density and strong covalence bondings. Our results indicate that ReN can be used as a potential ultra-incompressible conductor. In particular, a superconducting transition temperature is predicted as T c ≈ 4.8 K for NiAs-like ReN, which agrees well with the available experimental value.
International Journal of Modern Physics C, 2008
The elastic properties of rutile transition metal dioxides XO 2 (X = Ru, Rh, Os, and Ir) are inve... more The elastic properties of rutile transition metal dioxides XO 2 (X = Ru, Rh, Os, and Ir) are investigated using first-principles calculations based on density functional theory. Elastic constants, bulk modulus, shear modulus, and Young's modulus as well as Possion ratio are given. OsO 2 and IrO 2 show strong incompressibility. The hardness estimated for these dioxides shows that they are not superhard solids. The obtained Debye temperatures are comparative to those of transition metal dinitrides or diborides.
The Journal of Physical Chemistry C, 2010
For Li 2 FeSiO 4 , its P2 1 space group makes it possibly perfect as a new cathode material for L... more For Li 2 FeSiO 4 , its P2 1 space group makes it possibly perfect as a new cathode material for Li-ion batteries (Nishimura et al. J. Am. Chem. Soc. 2008, 130, 13212). For this type of Li 2 MSiO 4 (M ) Mn, Fe, and Co), the structural, electronic, and electrochemical properties have been investigated, using the density functional theory with the exchange-correlation energy treated as the generalized gradient approximation (GGA) plus on-site Coulomb energy correction (+U). Within the GGA+U framework, the fully lithiated Li 2 MSiO 4 as well as the delithiated LiMSiO 4 and MSiO 4 are all semiconducting, and the band gap lowers with the extraction of lithium ions. The fully lithiated compounds are all stabilized at their ferromagnetic phase, while the delithiated compounds are all stabilized when antiferromagnetic. Starting from the P2 1 structure, the fully delithiated MSiO 4 has better stability than that obtained from Pmn2 1 structure. In Li 2 FeSiO 4 , the possibility of reversibly extracting more than one lithium ion is enhanced because of the lower stability of the intermediate phase LiFeSiO 4 comparing with the Pmn2 1 symmetry situation. Li 2 MnSiO 4 with the P2 1 symmetry has higher electronic conductivity, and Li 2 CoSiO 4 has the suitable second-step voltage of less than 5.0 V. All Li 2 FeSiO 4 , Li 2 MnSiO 4 , and Li 2 CoSiO 4 are predicted as promising cathode materials.
Solid State Sciences, 2010
Aiming at the disputed ground state properties of perovskite (Pv) CaRuO 3 , we have investigated ... more Aiming at the disputed ground state properties of perovskite (Pv) CaRuO 3 , we have investigated the variations of electronic structures and magnetism between Pv and post-perovskite (PPv) phases of CaRuO 3 , based on the generalized gradient approximation (GGA) plus on-site Coulomb interaction U and spinorbital coupling (SOC) effect correction, namely GGA þ U þ SOC method. Both Pv and PPv phases have Mott-Hubbard insulating characteristics. Under Pnma symmetry, the 4d electrons have the stronger SOC effect and the weaker electronic correlation. Under Cmcm symmetry, however, the situation is just reversed. The G-type antiferromagnetic (AFM) superexchange interaction of RueRu is perfected in Pv phase, antiferromagnetically mediated by O atoms. PPv phase exhibits the AFM ground state along c direction, but the FMeAFM fluctuation exists in aeb plane of PPv phase. The strong magnetic anisotropy and big exchange constants are the inexistent evidences of spin-glass behavior in Pv and PPv phases. Ru 4þ is in low-spin state, S w 1. PvePPv phase transition changed the electronic and magnetic structures, but the magnetism is not sensitive to pressure in each phase. The suppression of ferromagnetism in Pv and PPv phases arises from the AFM interaction induced by the SOC effect and the FMeAFM fluctuation, respectively.
![Research paper thumbnail of 4d electronic and magnetic characteristics in postperovskite CaRuO[sub 3]](https://attachments.academia-assets.com/42644492/thumbnails/1.jpg)
](Journal of Applied Physics, 2010
The magnetic and electronic properties of postperovskite CaRuO 3 are investigated by performing t... more The magnetic and electronic properties of postperovskite CaRuO 3 are investigated by performing the first-principles calculation based on generalized gradient approximation plus parameter U method. A Mott-Hubbard insulating ground state with low spin Ru 4+ is found, and the A-type antiferromagnetic ͑AFM͒ spin ordering is preferred. Ru 4+ ions exhibit the spatially anisotropic exchange with the exchange in a-b plane weaker than that along c direction. The large Jahn-Teller distortion lowers the energy of d z 2 orbital, leading to the stabilization of low spin Ru 4+ and ferromagnetic ͑FM͒ orbital ordering. The transitions of metal-insulator and FM-AFM-FM depend on the Hubbard parameter U.
Chemical Physics Letters, 2010
The structural, elastic, electronic and dynamical properties of ReB and OsB are investigated by f... more The structural, elastic, electronic and dynamical properties of ReB and OsB are investigated by first-principles calculations based on density functional theory. It turns out that ReB and OsB are metallic ultraincompressible solids with small elastic anisotropy and high hardness. The change of c/a ratio in OsB indicates that there is a structural phase transition at about 31 GPa. Phonon spectra calculations show that both OsB and ReB are stable dynamically and there are abnormal phonon dispersions along special directions in Brillouin zone. OsB and ReB do not show superconductivity due to very weak electron-phonon interactions in them.
Chemical Physics Letters, 2009
The structural, elastic, and electronic properties of ReN 2 are investigated by first-principles ... more The structural, elastic, and electronic properties of ReN 2 are investigated by first-principles calculations with density functional theory. The obtained orthorhombic P bcn structure is energetically the most stable structure at ambient pressure. ReN 2 is a metallic, superincompressible solid and presents a rather elastic anisotropy. The estimated Debye temperature and hardness are 735 K and 17.1 GPa, respectively. Its estimated hardness is comparative to that of Si 3 N 4 .
Phosphorene has attracted intense interest due to its unexpected high carrier mobility and distin... more Phosphorene has attracted intense interest due to its unexpected high carrier mobility and distinguished anisotropic optoelectronic and electronic properties. In this work, we unraveled strain engineered phosphorene as a photocatalyst in the application of water splitting hydrogen production based on density functional theory calculations. Lattice dynamic calculations demonstrated the stability for such kind of artificial materials under different strains. The phosphorene lattice is unstable under compression strains and could be crashed, whereas phosphorene lattice shows very good stability under tensile strains. Further guarantee of the stability of phosphorene in liquid water is studied by ab initio molecular dynamics simulations. Tunable band gap from 1.54 eV at ambient condition to 1.82 eV under tensile strains for phosphorene is evaluated using parameter-free hybrid functional calculations. Appropriate band gaps and band edge alignments at certain pH demonstrate the potential application of phosphorene as a sufficiently efficient photocatalyst for visible light water splitting. We found that the strained phosphorene exhibits significantly improved photocatalytic properties under visible-light irradiation by calculating optical absorption spectra. Negative splitting energy of absorbed H2O indicates the water splitting on phosphorene is energy favorable both without and with strains.
The potential application of the single-layer MoS2 as a photocatalyst was revealed based on first... more The potential application of the single-layer MoS2 as a photocatalyst was revealed based on first-principles calculations. It is found that the pristine single-layer MoS2 is a good candidate for hydrogen production, and its catalysing ability can be tuned by the applied mechanical strain. Furthermore, the p-type doping could make the single layer a good photocatalyst for the overall water splitting.
Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or car... more Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp2-, and sp3-hybridized bonds. sp2-hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using an evolutionary algorithm in conjunction with ab initio method, we found that, under compression, dumbbell carbon in CaC2 can be polymerized first into 1D chain and then into ribbon and further into 2D graphite sheet at higher pressure. The C2/m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized in a wide pressure range of 15.2–105.8 GPa and then forced into MgB2-type phase with wide range stability up to at least 1 TPa. Strong electron–phonon coupling λ in compressed CaC2 is found, in particular for Immm phase, which has the highest λ value (0.562–0.564) among them, leading to its high superconducting critical temperature Tc (7.9∼9.8 K), which is comparable with the 11.5 K value of CaC6. Our results show that calcium not only can stabilize carbon sp2 hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline–earth metal carbides to uncover their peculiar physical properties under extreme conditions.
We study the electronic and lattice dynamical properties of compressed solid germane in the press... more We study the electronic and lattice dynamical properties of compressed solid germane in the pressure range up to 200 GPa with density functional theory. A stable metallic structure, Aba2, with a base-centered orthorhombic symmetry was found to be the lowest enthalpy phase for pressure from 23 to 177 GPa, suggesting an insulator to metal phase transition around 23 GPa. The Aba2 structure is predicted to have higher superconducting transition temperature than SiH4 reported recently, thus presenting new possibilities for exploring high temperature superconductivity in this hydrogen-rich system. 74.62.Fj, As suggested by Ashcroft [1], the dense hydrides of group IVa elements (C, Si, Ge, and Sn) are promising candidates for realizing metallization of solid hydrogen because hydrogen has already been "chemically precompressed". The metallization pressures in the group IVa hydrides are believed to be considerably lower than may be necessary for solid hydrogen. Ashcroft [1] also suggested that these hydrogen-rich alloys are likely superconductors with high transition temperatures T c . As put by Ginzburg [2], "high-temperature and roomtemperature superconductivity" and "metallic hydrogen and other exotic substances" are the two key "physical minima" at the beginning of the 21st century. Thus, exploring the possibility of metallic hydrogen and superconductivity has long been a major driving force in highpressure condensed matter science and remains an important challenge in modern physics. Recent experimental work on SiH 4 , using diamond-anvil cell techniques, has revealed an enhanced reflectivity with increasing pressure . It was found [3] that solid SiH 4 becomes opaque at 27-30 GPa and exhibits Drude-like behavior at around 60 GPa, signalling the onset of pressure-induced metallization. After Chen's experiment, Eremets et al reported that SiH 4 exhibits superconductivity at 96 and 120 GPa[4].
The Journal of Physical Chemistry C, 2012
Hydrogen-rich materials have fascinating physical and chemical properties such as various structu... more Hydrogen-rich materials have fascinating physical and chemical properties such as various structures and superconductivity under high-pressure. In this study, structural, electronic, dynamical, and superconducting properties of GeH 4 (H 2 ) 2 are investigated based on the first-principles calculations. We first predict several phase transitions of GeH 4 (H 2 ) 2 under pressure. Below 28 GPa, two degenerated structures with I4̅ m2 and Pmn2 1 symmetries are preferred, which can be viewed as the distortion of the experimentally observed fcc structure. Then, the GeH 4 (H 2 ) 2 , via a triclinic phase that stabilizes in the pressure range of 28−48 GPa, transforms into a metallic orthorhombic phase in which appears the metallization induced by pressure. Another metallic phase with P2 1 /c symmetry enters the phase diagram at around 220 GPa, which is more stable than the case of a decomposed material, and its stability is also confirmed by including the zero point energy correction. In the high-pressure P2 1 /c phase, the superconductivity is found, and the superconducting transition temperature is predicted to be as high as 76−90 K at 250 GPa. This superconductivity mainly results from the local vibrations of more H 2 units, though the vibration of Ge in an H 2 -formed grid also contributes to the electron−phonon interaction. This study is helpful for understanding the superconducting mechanism on hydrogen-rich compounds.
Journal of Superconductivity and Novel Magnetism, 2010
The electronic properties, lattice dynamics, and electron-phonon coupling of the Cmmm phase of Ge... more The electronic properties, lattice dynamics, and electron-phonon coupling of the Cmmm phase of GeH 4 have been studied by first-principle calculations using density functional perturbation theory. The electronic band structure shows the Cmmm phase metallic nature. It is found strong electron phonon interaction, and the superconducting critical temperature, predicted by Allen-Dynes modified McMillan equation, is about 40 K at 20 GPa.
EPL (Europhysics Letters), 2010
PACS 61.50.Ks -Crystallographic aspects of phase transformations; pressure effects PACS 71.15.Mb ... more PACS 61.50.Ks -Crystallographic aspects of phase transformations; pressure effects PACS 71.15.Mb -Density functional theory local density approximation, gradient and other corrections PACS 71.20.-b -Electron density of states and band structure of crystalline solids
The structural, dynamical, and electronic properties of compressed SrC 2 were systematically inve... more The structural, dynamical, and electronic properties of compressed SrC 2 were systematically investigated up to 200 GPa by using ab initio method. Three new phases are obtained by means of evolutionary algorithm. The confirmed most stable structure has C2/c symmetry at zero pressure, which transforms into an orthorhombic Cmcm phase at 4.5 GPa, followed by another orthorhombic Immm phase, which is stabilized at wide pressure range of 21.5-123.5 GPa, and then transformed into MgB 2 -type phase (space group, P6/mmm). Although SrC 2 has similar structural transformation to that of compressed CaC 2 , SrC 2 holds small electron-phonon coupling, which leads to its low superconducting critical temperature (only 1.8 K).
The structural, elastic and electronic properties of ReN are investigated by first-principles cal... more The structural, elastic and electronic properties of ReN are investigated by first-principles calculations based on density functional theory (DFT). The most stable structure of ReN is a NiAs-like structure, belonging to space group P6 3 /mmc with a = 2.7472 and c = 5.8180 Å. ReN is a metallic ultraincompressible solid and it exhibits low elastic anisotropy. Its linear incompressibility along the c-axis exceeds that of diamond. Its ultra-incompressibility is attributed to the high valence electron density and strong covalence bondings. Our results indicate that ReN can be used as a potential ultra-incompressible conductor. In particular, a superconducting transition temperature is predicted as T c ≈ 4.8 K for NiAs-like ReN, which agrees well with the available experimental value.
International Journal of Modern Physics C, 2008
The elastic properties of rutile transition metal dioxides XO 2 (X = Ru, Rh, Os, and Ir) are inve... more The elastic properties of rutile transition metal dioxides XO 2 (X = Ru, Rh, Os, and Ir) are investigated using first-principles calculations based on density functional theory. Elastic constants, bulk modulus, shear modulus, and Young's modulus as well as Possion ratio are given. OsO 2 and IrO 2 show strong incompressibility. The hardness estimated for these dioxides shows that they are not superhard solids. The obtained Debye temperatures are comparative to those of transition metal dinitrides or diborides.
The Journal of Physical Chemistry C, 2010
For Li 2 FeSiO 4 , its P2 1 space group makes it possibly perfect as a new cathode material for L... more For Li 2 FeSiO 4 , its P2 1 space group makes it possibly perfect as a new cathode material for Li-ion batteries (Nishimura et al. J. Am. Chem. Soc. 2008, 130, 13212). For this type of Li 2 MSiO 4 (M ) Mn, Fe, and Co), the structural, electronic, and electrochemical properties have been investigated, using the density functional theory with the exchange-correlation energy treated as the generalized gradient approximation (GGA) plus on-site Coulomb energy correction (+U). Within the GGA+U framework, the fully lithiated Li 2 MSiO 4 as well as the delithiated LiMSiO 4 and MSiO 4 are all semiconducting, and the band gap lowers with the extraction of lithium ions. The fully lithiated compounds are all stabilized at their ferromagnetic phase, while the delithiated compounds are all stabilized when antiferromagnetic. Starting from the P2 1 structure, the fully delithiated MSiO 4 has better stability than that obtained from Pmn2 1 structure. In Li 2 FeSiO 4 , the possibility of reversibly extracting more than one lithium ion is enhanced because of the lower stability of the intermediate phase LiFeSiO 4 comparing with the Pmn2 1 symmetry situation. Li 2 MnSiO 4 with the P2 1 symmetry has higher electronic conductivity, and Li 2 CoSiO 4 has the suitable second-step voltage of less than 5.0 V. All Li 2 FeSiO 4 , Li 2 MnSiO 4 , and Li 2 CoSiO 4 are predicted as promising cathode materials.
Solid State Sciences, 2010
Aiming at the disputed ground state properties of perovskite (Pv) CaRuO 3 , we have investigated ... more Aiming at the disputed ground state properties of perovskite (Pv) CaRuO 3 , we have investigated the variations of electronic structures and magnetism between Pv and post-perovskite (PPv) phases of CaRuO 3 , based on the generalized gradient approximation (GGA) plus on-site Coulomb interaction U and spinorbital coupling (SOC) effect correction, namely GGA þ U þ SOC method. Both Pv and PPv phases have Mott-Hubbard insulating characteristics. Under Pnma symmetry, the 4d electrons have the stronger SOC effect and the weaker electronic correlation. Under Cmcm symmetry, however, the situation is just reversed. The G-type antiferromagnetic (AFM) superexchange interaction of RueRu is perfected in Pv phase, antiferromagnetically mediated by O atoms. PPv phase exhibits the AFM ground state along c direction, but the FMeAFM fluctuation exists in aeb plane of PPv phase. The strong magnetic anisotropy and big exchange constants are the inexistent evidences of spin-glass behavior in Pv and PPv phases. Ru 4þ is in low-spin state, S w 1. PvePPv phase transition changed the electronic and magnetic structures, but the magnetism is not sensitive to pressure in each phase. The suppression of ferromagnetism in Pv and PPv phases arises from the AFM interaction induced by the SOC effect and the FMeAFM fluctuation, respectively.
Journal of Applied Physics, 2010
The magnetic and electronic properties of postperovskite CaRuO 3 are investigated by performing t... more The magnetic and electronic properties of postperovskite CaRuO 3 are investigated by performing the first-principles calculation based on generalized gradient approximation plus parameter U method. A Mott-Hubbard insulating ground state with low spin Ru 4+ is found, and the A-type antiferromagnetic ͑AFM͒ spin ordering is preferred. Ru 4+ ions exhibit the spatially anisotropic exchange with the exchange in a-b plane weaker than that along c direction. The large Jahn-Teller distortion lowers the energy of d z 2 orbital, leading to the stabilization of low spin Ru 4+ and ferromagnetic ͑FM͒ orbital ordering. The transitions of metal-insulator and FM-AFM-FM depend on the Hubbard parameter U.
Chemical Physics Letters, 2010
The structural, elastic, electronic and dynamical properties of ReB and OsB are investigated by f... more The structural, elastic, electronic and dynamical properties of ReB and OsB are investigated by first-principles calculations based on density functional theory. It turns out that ReB and OsB are metallic ultraincompressible solids with small elastic anisotropy and high hardness. The change of c/a ratio in OsB indicates that there is a structural phase transition at about 31 GPa. Phonon spectra calculations show that both OsB and ReB are stable dynamically and there are abnormal phonon dispersions along special directions in Brillouin zone. OsB and ReB do not show superconductivity due to very weak electron-phonon interactions in them.
Chemical Physics Letters, 2009
The structural, elastic, and electronic properties of ReN 2 are investigated by first-principles ... more The structural, elastic, and electronic properties of ReN 2 are investigated by first-principles calculations with density functional theory. The obtained orthorhombic P bcn structure is energetically the most stable structure at ambient pressure. ReN 2 is a metallic, superincompressible solid and presents a rather elastic anisotropy. The estimated Debye temperature and hardness are 735 K and 17.1 GPa, respectively. Its estimated hardness is comparative to that of Si 3 N 4 .
Phosphorene has attracted intense interest due to its unexpected high carrier mobility and distin... more Phosphorene has attracted intense interest due to its unexpected high carrier mobility and distinguished anisotropic optoelectronic and electronic properties. In this work, we unraveled strain engineered phosphorene as a photocatalyst in the application of water splitting hydrogen production based on density functional theory calculations. Lattice dynamic calculations demonstrated the stability for such kind of artificial materials under different strains. The phosphorene lattice is unstable under compression strains and could be crashed, whereas phosphorene lattice shows very good stability under tensile strains. Further guarantee of the stability of phosphorene in liquid water is studied by ab initio molecular dynamics simulations. Tunable band gap from 1.54 eV at ambient condition to 1.82 eV under tensile strains for phosphorene is evaluated using parameter-free hybrid functional calculations. Appropriate band gaps and band edge alignments at certain pH demonstrate the potential application of phosphorene as a sufficiently efficient photocatalyst for visible light water splitting. We found that the strained phosphorene exhibits significantly improved photocatalytic properties under visible-light irradiation by calculating optical absorption spectra. Negative splitting energy of absorbed H2O indicates the water splitting on phosphorene is energy favorable both without and with strains.
The potential application of the single-layer MoS2 as a photocatalyst was revealed based on first... more The potential application of the single-layer MoS2 as a photocatalyst was revealed based on first-principles calculations. It is found that the pristine single-layer MoS2 is a good candidate for hydrogen production, and its catalysing ability can be tuned by the applied mechanical strain. Furthermore, the p-type doping could make the single layer a good photocatalyst for the overall water splitting.
Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or car... more Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp2-, and sp3-hybridized bonds. sp2-hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using an evolutionary algorithm in conjunction with ab initio method, we found that, under compression, dumbbell carbon in CaC2 can be polymerized first into 1D chain and then into ribbon and further into 2D graphite sheet at higher pressure. The C2/m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized in a wide pressure range of 15.2–105.8 GPa and then forced into MgB2-type phase with wide range stability up to at least 1 TPa. Strong electron–phonon coupling λ in compressed CaC2 is found, in particular for Immm phase, which has the highest λ value (0.562–0.564) among them, leading to its high superconducting critical temperature Tc (7.9∼9.8 K), which is comparable with the 11.5 K value of CaC6. Our results show that calcium not only can stabilize carbon sp2 hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline–earth metal carbides to uncover their peculiar physical properties under extreme conditions.
We study the electronic and lattice dynamical properties of compressed solid germane in the press... more We study the electronic and lattice dynamical properties of compressed solid germane in the pressure range up to 200 GPa with density functional theory. A stable metallic structure, Aba2, with a base-centered orthorhombic symmetry was found to be the lowest enthalpy phase for pressure from 23 to 177 GPa, suggesting an insulator to metal phase transition around 23 GPa. The Aba2 structure is predicted to have higher superconducting transition temperature than SiH4 reported recently, thus presenting new possibilities for exploring high temperature superconductivity in this hydrogen-rich system. 74.62.Fj, As suggested by Ashcroft [1], the dense hydrides of group IVa elements (C, Si, Ge, and Sn) are promising candidates for realizing metallization of solid hydrogen because hydrogen has already been "chemically precompressed". The metallization pressures in the group IVa hydrides are believed to be considerably lower than may be necessary for solid hydrogen. Ashcroft [1] also suggested that these hydrogen-rich alloys are likely superconductors with high transition temperatures T c . As put by Ginzburg [2], "high-temperature and roomtemperature superconductivity" and "metallic hydrogen and other exotic substances" are the two key "physical minima" at the beginning of the 21st century. Thus, exploring the possibility of metallic hydrogen and superconductivity has long been a major driving force in highpressure condensed matter science and remains an important challenge in modern physics. Recent experimental work on SiH 4 , using diamond-anvil cell techniques, has revealed an enhanced reflectivity with increasing pressure . It was found [3] that solid SiH 4 becomes opaque at 27-30 GPa and exhibits Drude-like behavior at around 60 GPa, signalling the onset of pressure-induced metallization. After Chen's experiment, Eremets et al reported that SiH 4 exhibits superconductivity at 96 and 120 GPa[4].
The Journal of Physical Chemistry C, 2012
Hydrogen-rich materials have fascinating physical and chemical properties such as various structu... more Hydrogen-rich materials have fascinating physical and chemical properties such as various structures and superconductivity under high-pressure. In this study, structural, electronic, dynamical, and superconducting properties of GeH 4 (H 2 ) 2 are investigated based on the first-principles calculations. We first predict several phase transitions of GeH 4 (H 2 ) 2 under pressure. Below 28 GPa, two degenerated structures with I4̅ m2 and Pmn2 1 symmetries are preferred, which can be viewed as the distortion of the experimentally observed fcc structure. Then, the GeH 4 (H 2 ) 2 , via a triclinic phase that stabilizes in the pressure range of 28−48 GPa, transforms into a metallic orthorhombic phase in which appears the metallization induced by pressure. Another metallic phase with P2 1 /c symmetry enters the phase diagram at around 220 GPa, which is more stable than the case of a decomposed material, and its stability is also confirmed by including the zero point energy correction. In the high-pressure P2 1 /c phase, the superconductivity is found, and the superconducting transition temperature is predicted to be as high as 76−90 K at 250 GPa. This superconductivity mainly results from the local vibrations of more H 2 units, though the vibration of Ge in an H 2 -formed grid also contributes to the electron−phonon interaction. This study is helpful for understanding the superconducting mechanism on hydrogen-rich compounds.
Journal of Superconductivity and Novel Magnetism, 2010
The electronic properties, lattice dynamics, and electron-phonon coupling of the Cmmm phase of Ge... more The electronic properties, lattice dynamics, and electron-phonon coupling of the Cmmm phase of GeH 4 have been studied by first-principle calculations using density functional perturbation theory. The electronic band structure shows the Cmmm phase metallic nature. It is found strong electron phonon interaction, and the superconducting critical temperature, predicted by Allen-Dynes modified McMillan equation, is about 40 K at 20 GPa.
EPL (Europhysics Letters), 2010
PACS 61.50.Ks -Crystallographic aspects of phase transformations; pressure effects PACS 71.15.Mb ... more PACS 61.50.Ks -Crystallographic aspects of phase transformations; pressure effects PACS 71.15.Mb -Density functional theory local density approximation, gradient and other corrections PACS 71.20.-b -Electron density of states and band structure of crystalline solids