Show Posts
This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
HiThe mobility values are different from my calculation. For the method 1: Mobility = 2.81e+04 cm^2/(V*s) , For method 2: Mobility = 9.92e+04 cm^2/(V*s) .
I have been working on calculating the mobility of bilayer graphene using two different methods. However, I've encountered significant discrepancies in the mobility and carrier density values between the two approaches, even though I obtain similar results when applying these methods to single-layer graphene.
Below, I’ve outlined the two methods used along with their corresponding inputs and results. Could you please provide some guidance on what might be causing these differences?
Method 1:
# %% Load BulkConfiguration
a_brelaxdyn_bulk_configuration_1 = nlread(
filename=r'/home/energy/zhenlan/ATK/TBG/AB/ocu-mk/AB-relax-dyn.hdf5',
object_id='BulkConfiguration_1'
)[0]
# %% DynamicalMatrix
dynamical_matrix = DynamicalMatrix(
configuration=a_brelaxdyn_bulk_configuration_1,
filename='AB-mk-full-mo.hdf5',
object_id='dm',
repetitions=(9, 9, 1),
processes_per_displacement=8
)
dynamical_matrix.update()
# %% HamiltonianDerivatives
hamiltonian_derivatives = HamiltonianDerivatives(
configuration=a_brelaxdyn_bulk_configuration_1,
filename='AB-mk-full-mo.hdf5',
object_id='hd',
repetitions=(9, 9, 1),
processes_per_displacement=8
)
hamiltonian_derivatives.update()
# %% ElectronPhononCoupling
kpoints_fractional = RegularKpointGrid(
ka_range=(0.313333, 0.353333),
kb_range=(0.313333, 0.353333),
na=20,
nb=20
)
qpoints_fractional = RegularKpointGrid(
ka_range=(-0.04, 0.04),
kb_range=(-0.04, 0.04),
na=40,
nb=40
)
electron_phonon_coupling = ElectronPhononCoupling(
configuration=a_brelaxdyn_bulk_configuration_1,
hamiltonian_derivatives=hamiltonian_derivatives,
dynamical_matrix=dynamical_matrix,
kpoints_fractional=kpoints_fractional,
qpoints_fractional=qpoints_fractional,
electron_bands=frozenset({8, 7}),
energy_tolerance=0.01*eV,
initial_state_energy_range=[-0.5, 0.5]*eV
)
nlsave('AB-mk-full-mo.hdf5', electron_phonon_coupling)
# %% Mobility (Full)
mobility = Mobility(
configuration=a_brelaxdyn_bulk_configuration_1,
electron_phonon_coupling=electron_phonon_coupling,
fermi_shift=0.13*eV,
integration_method=GaussianBroadening(
broadening=0.003*eV
),
calculate_hall_coefficients=False
)
nlsave('AB-mk-full-mo.hdf5', mobility)
and the mobility txt file is
Mobility_0@AB-mk-full-mo.hdf5
+------------------------------------------------------------------------------+
| Mobility Report |
| ---------------------------------------------------------------------------- |
| Input parameters: |
| Temperature = 300.00 K |
| Fermi level shift = 0.13 eV |
| Energy broadening = 0.0030 eV |
| q-grid refinement = 1 |
| |
+------------------------------------------------------------------------------+
| Trace of linear responce tensors: |
+------------------------------------------------------------------------------+
| |
| Electrons: |
| |
| Mobility = 2.81e+04 cm^2/(V*s) |
| Conductivity = 1.40e+01 S/m |
| Seebeck coefficient = -3.18e-05 V/K |
| Thermal conductivity = 5.65e-05 W/(m*K) |
| Carrier density (2D, xy) = 6.52e+06 cm^-2 |
| |
| |
| Holes: |
| |
| Mobility = 5.41e-05 cm^2/(V*s) |
| Conductivity = 1.38e-02 S/m |
| Seebeck coefficient = 1.29e-03 V/K |
| Thermal conductivity = 1.79e-06 W/(m*K) |
| Carrier density (2D, xy) = 3.35e+12 cm^-2
Method 2:
step 1：
# %% Load BulkConfiguration
a_brelaxdyn_bulk_configuration_1 = nlread(
filename=r'/home/energy/zhenlan/ATK/TBG/AB/ocu-mk/AB-relax-dyn.hdf5',
object_id='BulkConfiguration_1'
)[0]
# %% DynamicalMatrix
dynamical_matrix = DynamicalMatrix(
configuration=a_brelaxdyn_bulk_configuration_1,
filename='AB-mk-full-mo.hdf5',
object_id='dm',
repetitions=(9, 9, 1),
processes_per_displacement=8
)
dynamical_matrix.update()
# %% HamiltonianDerivatives
hamiltonian_derivatives = HamiltonianDerivatives(
configuration=a_brelaxdyn_bulk_configuration_1,
filename='AB-mk-full-mo.hdf5',
object_id='hd',
repetitions=(9, 9, 1),
processes_per_displacement=8
)
hamiltonian_derivatives.update()
# %% ElectronPhononCoupling
kpoints_fractional = RegularKpointGrid(
ka_range=(0.313333, 0.353333),
kb_range=(0.313333, 0.353333),
na=20,
nb=1
)
qpoints_fractional = RegularKpointGrid(
ka_range=(-0.04, 0.04),
kb_range=(-0.04, 0.04),
na=40,
nb=40
)
electron_phonon_coupling = ElectronPhononCoupling(
configuration=a_brelaxdyn_bulk_configuration_1,
hamiltonian_derivatives=hamiltonian_derivatives,
dynamical_matrix=dynamical_matrix,
kpoints_fractional=kpoints_fractional,
qpoints_fractional=qpoints_fractional,
electron_bands=frozenset({8, 7}),
energy_tolerance=0.01*eV,
initial_state_energy_range=[-0.5, 0.5]*eV
)
nlsave('AB-mk-full-mo.hdf5', electron_phonon_coupling)
# %% Mobility (Full)
mobility = Mobility(
configuration=a_brelaxdyn_bulk_configuration_1,
electron_phonon_coupling=electron_phonon_coupling,
fermi_shift=0.13*eV,
integration_method=GaussianBroadening(
broadening=0.003*eV
),
calculate_hall_coefficients=False
)
nlsave('AB-mk-full-mo.hdf5', mobility)
step2:
# %% Load BulkConfiguration
a_brelaxdyn_bulk_configuration_1 = nlread(
filename=r'/home/energy/zhenlan/ATK/TBG/AB/ocu-mk/AB-relax-dyn.hdf5',
object_id='BulkConfiguration_1'
)[0]
mobility_full = nlread('AB-mk-full-mo.hdf5', Mobility)[0]
# %% Mobility (Isotropic)
kpoints = MonkhorstPackGrid(
na=99,
nb=99,
nc=1
)
mobility = Mobility(
configuration=a_brelaxdyn_bulk_configuration_1,
kpoints=kpoints,
method=Isotropic,
fermi_shift=0.13*eV,
mobility_object=mobility_full,
inverse_relaxation_time=numpy.linspace(0, 1e+12, 100)*Second**-1,
integration_method=GaussianBroadening(
broadening=0.003*eV
),
energies=numpy.linspace(-0.24, 0.24, 100)*eV,
calculate_hall_coefficients=False
)
nlsave('AB-mu-line-iso.hdf5', mobility)
mobility results:
+------------------------------------------------------------------------------+
| Mobility Report |
| ---------------------------------------------------------------------------- |
| Input parameters: |
| Temperature = 300.00 K |
| Fermi level shift = 0.13 eV |
| Energy broadening = 0.0030 eV |
| q-grid refinement = 1 |
| |
+------------------------------------------------------------------------------+
| Trace of linear responce tensors: |
+------------------------------------------------------------------------------+
| |
| Electrons: |
| |
| Mobility = 9.92e+04 cm^2/(V*s) |
| Conductivity = 2.10e+07 S/m |
| Seebeck coefficient = 5.71e-05 V/K |
| Thermal conductivity = 8.37e+01 W/(m*K) |
| Carrier density (2D, xy) = 2.77e+12 cm^-2 |
| |
| |
| Holes: |
| |
| Mobility = 4.29e+05 cm^2/(V*s) |
| Conductivity = 8.30e+04 S/m |
| Seebeck coefficient = 1.22e-03 V/K |
| Thermal conductivity = 9.48e+00 W/(m*K) |
| Carrier density (2D, xy) = 2.54e+09 cm^-2 |
|
The relaxed structures input are attached for your reference.
Could you please help me understand the cause of these discrepancies, particularly in the bilayer graphene results? Any insight would be greatly appreciated.
Best regards,
ZY
