Supporting Information Half-metallic ferromagnetism and surface ...
Supporting Information
Half-metallic ferromagnetism and surface functionalization-induced metal-insulator transition in graphene-like two-dimensional Cr2C crystals
Chen Si†, Jian Zhou†, and Zhimei Sun* †, ‡ †
School of Materials Science and Engineering, Beihang University, Beijing 100191, China
‡
Center for Integrated Computational Materials Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, China
* Corresponding author: [email protected]
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1. Structural stabilities of Cr2C and Cr2CT2 (T=F, OH, H or Cl) MXenes The phonon spectra of Cr2C and Cr2CT2 (T=F, OH, H or Cl) MXenes are calculated using the Phonopy code1 interfaced with the density functional perturbation theory2 implemented in VASP. Because the phonon calculations using HSE functional are quite expensive, here we use GGA+U (with an onsite Hubbard U correction of 3 eV for the Cr d electrons3) for the phonon calculations. The calculated phonon spectra are shown in Figure S1. The absence of negative frequencies clearly demonstrates that Cr2C and Cr2CT2 (T=F, OH, H or Cl) MXenes are structurally stable.
Figure S1. The phonon spectra for Cr2C (a), Cr2CF2 (b), Cr2C(OH)2 (c), Cr2CH2 (d) and Cr2CCl2 (e) MXenes.
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2. The robustness of the magnetic properties of Cr2C MXene at room temperature
To examine whether the magnetic state of Cr2C MXene survives at room temperature, we have built a large 4×4 supercell, and performed spin-polarized ab initio molecular dynamics (MD) simulations with a Nose-Hoover thermostat at 300K and a time step of 2 fs. Considered that the MD simulations using HSE functional are very expensive, here we use GGA+U (with an onsite Hubbard U correction of 3 eV for the Cr d electrons3) for the ab initio MD simulations. Figure S2(a) and (b) display the fluctuations of the temperature and the magnetic moment as a function of the simulation time at 300 K, respectively. After 10 ps, no structural deformation is observed, suggesting that Cr2C is thermally stable at room temperature. Most importantly, the system remains magnetic with an average magnetic moment of around 128 µΒ (corresponding to 8 µΒ per unitcell) at 300 K. This to say, the magnetic state of Cr2C is robust at the room temperature.
Figure S2. The fluctuations of temperature (a) and magnetic moment (b) as a function of the MD simulation time at 300 K.
References: 1. Parlinski, K.; Li, Z.; Kawazoe, Y. First-principles Determination of the Soft Mode in Cubic ZrO2. Phys. Rev. Lett. 1997, 78, 4063. 2. Gonze, X.; Lee, C. Dynamical Matrices, Born Effective Charges, Dielectric Permittivity Tensors, and Interatomic Force Constants from Density-functional Perturbation Theory. Phys. Rev. B 1997, 55, 10355.
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3. Korotin, M. A.; Anisimov, V. I.; Khomskii, D. I.; Sawatzky, G. A. CrO2: a Selfdoped Double Exchange Ferromagnet. Phy. Rev. Lett. 1998, 80, 4305.
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Half-metallic ferromagnetism and surface functionalization-induced metal-insulator transition in graphene-like two-dimensional Cr2C crystals
Chen Si†, Jian Zhou†, and Zhimei Sun* †, ‡ †
School of Materials Science and Engineering, Beihang University, Beijing 100191, China
‡
Center for Integrated Computational Materials Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, China
* Corresponding author: [email protected]
S-1
1. Structural stabilities of Cr2C and Cr2CT2 (T=F, OH, H or Cl) MXenes The phonon spectra of Cr2C and Cr2CT2 (T=F, OH, H or Cl) MXenes are calculated using the Phonopy code1 interfaced with the density functional perturbation theory2 implemented in VASP. Because the phonon calculations using HSE functional are quite expensive, here we use GGA+U (with an onsite Hubbard U correction of 3 eV for the Cr d electrons3) for the phonon calculations. The calculated phonon spectra are shown in Figure S1. The absence of negative frequencies clearly demonstrates that Cr2C and Cr2CT2 (T=F, OH, H or Cl) MXenes are structurally stable.
Figure S1. The phonon spectra for Cr2C (a), Cr2CF2 (b), Cr2C(OH)2 (c), Cr2CH2 (d) and Cr2CCl2 (e) MXenes.
S-2
2. The robustness of the magnetic properties of Cr2C MXene at room temperature
To examine whether the magnetic state of Cr2C MXene survives at room temperature, we have built a large 4×4 supercell, and performed spin-polarized ab initio molecular dynamics (MD) simulations with a Nose-Hoover thermostat at 300K and a time step of 2 fs. Considered that the MD simulations using HSE functional are very expensive, here we use GGA+U (with an onsite Hubbard U correction of 3 eV for the Cr d electrons3) for the ab initio MD simulations. Figure S2(a) and (b) display the fluctuations of the temperature and the magnetic moment as a function of the simulation time at 300 K, respectively. After 10 ps, no structural deformation is observed, suggesting that Cr2C is thermally stable at room temperature. Most importantly, the system remains magnetic with an average magnetic moment of around 128 µΒ (corresponding to 8 µΒ per unitcell) at 300 K. This to say, the magnetic state of Cr2C is robust at the room temperature.
Figure S2. The fluctuations of temperature (a) and magnetic moment (b) as a function of the MD simulation time at 300 K.
References: 1. Parlinski, K.; Li, Z.; Kawazoe, Y. First-principles Determination of the Soft Mode in Cubic ZrO2. Phys. Rev. Lett. 1997, 78, 4063. 2. Gonze, X.; Lee, C. Dynamical Matrices, Born Effective Charges, Dielectric Permittivity Tensors, and Interatomic Force Constants from Density-functional Perturbation Theory. Phys. Rev. B 1997, 55, 10355.
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3. Korotin, M. A.; Anisimov, V. I.; Khomskii, D. I.; Sawatzky, G. A. CrO2: a Selfdoped Double Exchange Ferromagnet. Phy. Rev. Lett. 1998, 80, 4305.
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