### 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.

### Messages - beauyy

Pages: [1] 2 3
1
##### General Questions / Re: the physical definition of the Fermi level in band structure calculation
« on: May 23, 2020, 03:57 »
Is it accurate to calculate the position of the Fermi level by ATK-DFT: LCAO? Typically DFT codes fail to accurately define the Fermi level position which can actually be placed anywhere within the gap.

2
##### General Questions / the physical definition of the Fermi level in band structure calculation
« on: May 21, 2020, 13:46 »
What is the physical definition of the Fermi level in band structure calculation? Can I use the relative distance from CBM and VBM to the Fermi level to  estimate the conduction type or doping type ?

3
##### Questions and Answers / Re: phosphorene nanotube optimization
« on: May 13, 2016, 12:30 »
So do you think that the x and y directions should be constrained? Before DFBT, I also used DFT to optimize the structure, similar phenomenon happened.  And I found that the structure suddenly had a great change after max_forces is less than 0.5 eV/Ang.

4
##### Questions and Answers / phosphorene nanotube optimization
« on: May 13, 2016, 06:49 »
Dear sir,
I built a phosphorene nanotube and optimized it. But during the optimization process, the structure was difficult to converge and all the P atoms were discreted from the bulk. T The .py file is attached as following. What's wrong with my optimization parameter?

# -------------------------------------------------------------
# Bulk configuration
# -------------------------------------------------------------

# Set up lattice
vector_a = [44.2622, 0.0, 0.0]*Angstrom
vector_b = [0.0, 44.2622, 0.0]*Angstrom
vector_c = [0.0, 0.0, 3.31586338739]*Angstrom
lattice = UnitCell(vector_a, vector_b, vector_c)

# Define elements
elements = [Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus]

# Define coordinates
fractional_coordinates = [[ 0.36582515,  0.48499453,  0.25000081],
[ 0.47283227,  0.3677228 ,  0.25000081],
[ 0.61743134,  0.43325366,  0.25000081],
[ 0.59979135,  0.5910257 ,  0.25000081],
[ 0.44429017,  0.62300331,  0.25000081],
[ 0.44429017,  0.37699669,  0.74999917],
[ 0.59979135,  0.4089743 ,  0.74999917],
[ 0.61743134,  0.56674634,  0.74999917],
[ 0.47283227,  0.6322772 ,  0.74999917],
[ 0.36582515,  0.51500547,  0.74999917],
[ 0.40783012,  0.34090592,  0.74999943],
[ 0.62284893,  0.36314607,  0.74999943],
[ 0.66814176,  0.57451369,  0.74999943],
[ 0.48111546,  0.68290592,  0.74999943],
[ 0.32023402,  0.53852838,  0.74999943],
[ 0.37712092,  0.36338569,  0.24999903],
[ 0.59197975,  0.34088652,  0.24999903],
[ 0.67977275,  0.53827678,  0.24999903],
[ 0.51917299,  0.68276983,  0.24999903],
[ 0.33212387,  0.57468119,  0.24999903],
[ 0.40044368,  0.40909823,  0.24999996],
[ 0.55571165,  0.37719373,  0.24999996],
[ 0.63403508,  0.51500332,  0.24999996],
[ 0.52717365,  0.63207883,  0.24999996],
[ 0.38280622,  0.56662589,  0.24999996],
[ 0.38280623,  0.43337411,  0.75000002],
[ 0.52717365,  0.36792117,  0.75000002],
[ 0.63403508,  0.48499668,  0.75000002],
[ 0.55571165,  0.62280626,  0.75000002],
[ 0.40044368,  0.59090176,  0.75000002],
[ 0.33212387,  0.42531881,  0.75000097],
[ 0.51917299,  0.31723017,  0.75000097],
[ 0.67977275,  0.46172322,  0.75000097],
[ 0.59197974,  0.65911348,  0.75000097],
[ 0.37712092,  0.63661431,  0.75000097],
[ 0.32023402,  0.46147161,  0.25000057],
[ 0.48111546,  0.31709408,  0.25000057],
[ 0.66814176,  0.42548631,  0.25000057],
[ 0.62284892,  0.63685393,  0.25000057],
[ 0.40783012,  0.65909408,  0.25000057]]

# Set up configuration
bulk_configuration = BulkConfiguration(
bravais_lattice=lattice,
elements=elements,
fractional_coordinates=fractional_coordinates
)

# -------------------------------------------------------------
# Calculator
# -------------------------------------------------------------
#----------------------------------------
# Basis Set
#----------------------------------------
basis_set = DFTBDirectory("dftb/mio/")

#----------------------------------------
# Pair Potentials
#----------------------------------------
pair_potentials = DFTBDirectory("dftb/mio/")

numerical_accuracy_parameters = NumericalAccuracyParameters(
k_point_sampling=(1, 1, 10),
density_mesh_cutoff=200.0*Hartree,
)

iteration_control_parameters = IterationControlParameters()

poisson_solver = MultigridSolver(
boundary_conditions=[[NeumannBoundaryCondition,NeumannBoundaryCondition],
[NeumannBoundaryCondition,NeumannBoundaryCondition],
[PeriodicBoundaryCondition,PeriodicBoundaryCondition]]
)

calculator = SlaterKosterCalculator(
basis_set=basis_set,
pair_potentials=pair_potentials,
numerical_accuracy_parameters=numerical_accuracy_parameters,
iteration_control_parameters=iteration_control_parameters,
poisson_solver=poisson_solver,
)

bulk_configuration.setCalculator(calculator)
nlprint(bulk_configuration)
bulk_configuration.update()
nlsave('F:/P/P-AsP/bs-P-tube-40-dftb-0.2.nc', bulk_configuration)

bulk_configuration = OptimizeGeometry(
bulk_configuration,
max_forces=0.2*eV/Ang,
max_stress=0.2*eV/Ang**3,
max_steps=200,
max_step_length=0.2*Ang,
trajectory_filename=None,
optimizer_method=QuasiNewton(),
)
nlsave('F:/P/P-AsP/bs-P-tube-40-dftb-0.2.nc', bulk_configuration)
nlprint(bulk_configuration)

5
##### Questions and Answers / eliminate dangling bond
« on: December 24, 2015, 04:48 »
How can I eliminate the dangling bond at the surface of ZnO sheet?
I mean the method except passivating  dangling bond by H atoms, or the other atoms.

6
##### Questions and Answers / transmission eigenstate of AsP nanoribbon
« on: November 27, 2015, 03:45 »
Hi, all!
I calculated the current of AsP nanoribbon under different directions. The current curves show that the zigzag current is higher than that in armchair direction. But the transmission eigenstate shows an opposite trend. Can anyone interpret it for me ? The energy is 0 eV, quantum number is 2, and ka, kb are 0.5 for the calculation of transmission eigenstate.

7
##### Questions and Answers / Re: phonon bandstructure of phosphorene with ATK-Classical method
« on: August 27, 2015, 13:52 »
When I decreased the bulk of monolayer phosphorene into that contains 4 P atoms in a bulk, the negative bands vanshied. But the same phenomenon didn't happen in other 2D material, for example, Arsenene. Why?

8
##### Questions and Answers / phonon bandstructure of phosphorene with ATK-Classical method
« on: August 27, 2015, 07:01 »
Dear sir,
I tried to calculate the phonon bandstructure of monolayer phosphorene with ATK-Classical method, but there were  negative bands. The bulk had been optimized to Max force less than 0.001 eV/A and Max stress less than 0.001 eV/A. How can I eliminate the negative bands?
# -------------------------------------------------------------
# Bulk configuration
# -------------------------------------------------------------

# Set up lattice
vector_a = [6.68209223283, 0.0, 0.0]*Angstrom
vector_b = [0.0, 9.16633794912, 0.0]*Angstrom
vector_c = [0.0, 0.0, 40.0]*Angstrom
lattice = UnitCell(vector_a, vector_b, vector_c)

# Define elements
elements = [Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus, Phosphorus, Phosphorus, Phosphorus, Phosphorus,
Phosphorus]

# Define coordinates
fractional_coordinates = [[ 0.24999996,  0.25000008,  0.44609425],
[ 0.        ,  0.41331253,  0.44609424],
[ 0.50000005,  0.4133125 ,  0.44609424],
[ 0.24999996,  0.74999997,  0.44609422],
[ 0.75      ,  0.74999994,  0.44609423],
[ 0.00000001,  0.91331268,  0.44609425],
[ 0.50000005,  0.91331264,  0.44609424],
[ 0.74999999,  0.25000003,  0.44609426],
[ 0.        ,  0.        ,  0.5       ],
[ 0.50000005,  0.00000003,  0.5       ],
[ 0.24999996,  0.16331255,  0.49999999],
[ 0.74999999,  0.1633126 ,  0.49999998],
[ 0.00000001,  0.49999985,  0.49999999],
[ 0.50000005,  0.49999989,  0.5       ],
[ 0.24999996,  0.66331266,  0.50000002],
[ 0.75      ,  0.66331269,  0.50000001]]

# Set up configuration
bulk_configuration = BulkConfiguration(
bravais_lattice=lattice,
elements=elements,
fractional_coordinates=fractional_coordinates
)

# -------------------------------------------------------------
# Calculator
# -------------------------------------------------------------

potentialSet = EAMFS_FeP_2004()
calculator = TremoloXCalculator(parameters=potentialSet)

bulk_configuration.setCalculator(calculator)
nlprint(bulk_configuration)
bulk_configuration.update()
nlsave('F:/P-As/pb-P.nc', bulk_configuration)

bulk_configuration = OptimizeGeometry(
bulk_configuration,
max_forces=0.001*eV/Ang,
max_stress=0.001*eV/Ang**3,
max_steps=200,
max_step_length=0.2*Ang,
trajectory_filename=None,
optimizer_method=LBFGS(),
)
nlsave('F:/P-As/pb-P.nc', bulk_configuration)
nlprint(bulk_configuration)

# -------------------------------------------------------------
# Phonon bandstructure
# -------------------------------------------------------------
phonon_bandstructure = PhononBandstructure(
configuration=bulk_configuration,
route=['G', 'X', 'Y', 'Z', 'G'],
points_per_segment=100,
number_of_bands=20
)
nlsave('F:/P-As/pb-P.nc', bulk_configuration)
nlsave('F:/P-As/pb-P.nc', phonon_bandstructure)

9
##### Questions and Answers / Calculation of phonon bandstructure of 2D materials
« on: July 30, 2015, 05:35 »
Dear sir,
I am calculating the phonon bandstricture of 2D materials with ATK 13.8.1. It spends too much time for calculating it by ATK-DFT. Do you have any method to save the time? What is the accurancy difference between ATK-DFT and ATK-classical in calculating phonon bandstructure?

10
##### Questions and Answers / Re: Optimization of c-parameter in MGGA
« on: July 27, 2015, 08:23 »
So in the situration that the bandgap of  other 2D material that has no  literature value, I can only use GGA  to get the relative value when they are compared between different Xes, or under different uniaxial stresses, altuhough the result caculated by GGA is underestimated?

11
##### Questions and Answers / Re: Optimization of c-parameter in MGGA
« on: July 25, 2015, 04:04 »
I am comparing the bandgaps of a series of Molybdenum dichalcogenides (MoX2; X=S, Se, Te). Should they be compared with the same c-paramter value? Or should their c-parameters be optimized respectively?
If they are optimized respectively, does their bandgaps can be compared to each other?

12
##### Questions and Answers / Optimization of c-parameter in MGGA
« on: July 24, 2015, 12:41 »
Dear sir,
How can I optimize c-parameter in MGGA when the experimental or HSE06 values of bandgap are unavailable?

13
##### Questions and Answers / Re: optomization of monolayer silicene device
« on: July 17, 2015, 07:42 »
Is the geometry of monolayer silicence unavailable under the higher bias than 1.4 V ?

14
##### Questions and Answers / Re: optomization of monolayer silicene device
« on: July 14, 2015, 10:27 »
The geometric optimization under 1.4 V is easy to achieve full SCF. The geometry is the same to that under zero bias. But when I  do the geometeic optimization  under 1.6 V, it is hard to reach full SCF whatever the original geometry is under zero or 1.4 V. It is a big trouble to me.

15
##### Questions and Answers / Re: optomization of monolayer silicene device
« on: July 11, 2015, 05:50 »
Thanks for your reply.  I find that the structure of monolayer silicene can easily to achieve SCF under lower bias,  but the monolayer silicene is still difficult to achieve SCF under 1.6 V when I use the optimized structure under 1.4 V. What can I do for this problem?

Pages: [1] 2 3