How to calculate electron phonon coupling const.( lambda) for superconducting temperature calculation.

[Kuldeep_kargeti]

Dear Developers,

I wanted to know if it is possible to calculate electron phonon coupling constant (lambda) which can be used to calculate superconducting temperature for the material under observation. I am using vasp-6.5.0 for
my calculations.
Please help me with the necessary steps to get this coupling constant.

I have generated the phelel_params.hdf5 file using this tag ELPH_POT_GENERATE and now i am using the following INCAR file for carrying out the electron phonon coupling calculations.

Startparameter for this Run:
ISTART = 0 job : 0-new 1-cont 2-samecut
PREC = Accurate

Electronic Relaxation 1
NELM = 250
EDIFF = 1E-06 stopping-criterion for ELM
LORBIT = 11

Magnetic Calculation
ISPIN = 1

ISMEAR= -5
LWAVE=.False.
ENCUT=550
IALGO = 38 algorithm
KPAR = 8

##IBRION = 6 ( this I used in previous step to get the electron phonon potential from finite difference routine)
ELPH_POT_FFT_MESH = 60 60 48
##ELPH_POT_GENERATE = True ( used in previous step with IBRION = 6 to generate phelel_param.hdf5 file)
ELPH_RUN = True.
ELPH_KPAR= 4
ELPH_DRIVER = mels
ELPH_KSPACING= 0.5

Will it give also generate lambda value in the OUTCAR file.

Looking forward to your response.

[marie-therese.huebsch]

Hello,

I am afraid as of VASP 6.5.1 we do not support a feature to compute the superconducting temperature. You may do your own postprocessing of the electron-phonon matrix elements using ELPH_DRIVER.

But we are working on including this in a future release.

Best regards,
Marie-Therese

[Kuldeep_kargeti]

Thanks for the reply.

As you can see, I have used ELPH_DRIVER = mels in INCAR file but it did not generate vaspelph.h5 file.

Later I also used ELPH_DECOMPOSE = VDPR and ELPH_DRIVER = mels both in the INCAR file but it also did not write vaspelph.h5 file.

Am I missing something in the INCAR file.

I checked OUTCAR file and I found this,

Matrix elements:
v d r p q s
elph_decompose = T T T T F F
elph_lr = T
elph_writemels = F

Please help with generating the electron -phonon matrix elements.

[marie-therese.huebsch]

To reply to questions on your specific calculation, could you please upload a minimal reproducible example as suggested in the forum guidelines? Cheers