QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: njuxyh on June 28, 2014, 01:26

Title: strange thing about Phonon: Automatically detected repetitions
Post by: njuxyh on June 28, 2014, 01:26

i have a 1D structure(Z-periodic), and want to calculate the phonon bandstructure and dos. i set the cell size

 vector_a = [15.0, 0.0, 0.0]*Angstrom
vector_b = [0.0, 50.0, 0.0]*Angstrom
vector_c = [0.0, 0.0, 3.30101]*Angstrom


the vector a is set 15, because i have tested 15 angstrom is enough to screen the neighbour interaction
but the output writes:

Phonon: Automatically detected repetitions = [3 1 7]             


i think 3 is too big, it should be 1, otherwise, the computational time is long.

the i set the vector a  is 50,

but the output is still (3,1,7)

so i am wondering how to set the vector a, and make the auto detected repetitions is (1,1 7)?

ps: the kpoint is:(1,1 5),is it ok?


the exchange_correlation = GGA.PBE

numerical_accuracy_parameters = NumericalAccuracyParameters(
    k_point_sampling=(1, 1, 5),
    )

Title: Re: strange thing about Phonon: Automatically detected repetitions
Post by: kstokbro on June 29, 2014, 01:28

The default detection is currently often too conservative,  however, you can control the repetition using dynamical_matrix_parameters

dynamical_matrix_parameters = DynamicalMatrixParameters(
    repeats=(1,5,3),
    )
calculator = LCAOCalculator(
    dynamical_matrix_parameters=dynamical_matrix_parameters)

Title: Re: strange thing about Phonon: Automatically detected repetitions
Post by: njuxyh on June 30, 2014, 05:46

Quote from: kstokbro on June 29, 2014, 01:28

The default detection is currently often too conservative,  however, you can control the repetition using dynamical_matrix_parameters

dynamical_matrix_parameters = DynamicalMatrixParameters(
    repeats=(1,5,3),
    )
calculator = LCAOCalculator(
    dynamical_matrix_parameters=dynamical_matrix_parameters)

i add the following line into the script:
dynamical_matrix_parameters = DynamicalMatrixParameters(
        repeats=(1,1,7),
        atomic_displacement=0.01*Ang
        )
 and insert the corresponding line to the calcultor:
calculator = LCAOCalculator(
    basis_set=basis_set,
    exchange_correlation=exchange_correlation,
    numerical_accuracy_parameters=numerical_accuracy_parameters,
    dynamical_matrix_parameters=dynamical_matrix_parameters
    )

is that so ?

ps: if i want to calculate the phonon  transmission spectrum of a device, i think, the first step is also to calculate phonon bandstructure, so how to
set the same parameter to control the repeat for a device ?