[QE-users] Lambda ad Tc for Pb(111)
Maciej Szary
maciej.szary at put.poznan.pl
Mon Jun 15 14:53:01 CEST 2020
Dear Professor Giannozzi,
sorry if I didn't specify. "NaN" referred explicitly to Tc calculations
done by lambda.x. I do a pw.x calculation and I get a convergence, ph.x
run is rather long, still it produces positive frequencies e.g.
/
// **************************************************************************//
// freq ( 1) = 0.819632 [THz] = 27.339964 [cm-1]//
// freq ( 2) = 0.914078 [THz] = 30.490364 [cm-1]//
//...//
// freq ( 18) = 2.063295 [THz] = 68.824112 [cm-1]/
/ **************************************************************************/
Next I use q2r.x. I do get some warnings e.g.:
/ Broadening = 0.005//
// q-space grid ok, #points = 36//
//
// fft-check warning: sum of imaginary terms = 3.497134E-06/
but based on the previous forum posts, this seems acceptable.
Subsequently I use matdyn.x and get lambda file containing:
/
// Broadening 0.0050 lambda 1.7637 dos(Ef) 21.5379 omega_ln
[K] 49.4388//
// Broadening 0.0100 lambda 1.7028 dos(Ef) 21.2277 omega_ln
[K] 49.7600//
//...////
// Broadening 0.0500 lambda 1.7499 dos(Ef) 22.1428 omega_ln
[K] 48.1738/
(shouldn't this be enough to calculate Tc using McMillan formula?)
Finally I use lambda.x and get:
/
// lambda = NaN ( NaN ) <log w>= NaN K N(Ef)=
21.537940 at degauss= 0.005//
// lambda = NaN ( NaN ) <log w>= NaN K N(Ef)=
21.227733 at degauss= 0.010//
//...//
// lambda = NaN ( NaN ) <log w>= NaN K N(Ef)=
22.142765 at degauss= 0.050//
//lambda omega_log T_c//
// NaN NaN NaN//
// NaN NaN NaN//
//...//
// NaN NaN NaN/
I've been redoing this procedure, with different parameters listed in my
previous email.
Regards,
Maciej Szary
--
Research Assistant,
Institute of Physics,
Poznan University of Technology
Piotrowo 3A, 61-138 Poznan
On 6/14/20 3:50 PM, Maciej Szary wrote:
> Dear QE users,
>
> I'm trying to calculate electron-phonon coefficient and the critical
> superconducting temperature of Pb(111). As an introduction I've done
> the [PHonon/examples/example03] (bulk Al), and I've reproduced the
> results successfully. However, in case of Pb(111), I can't get Tc for
> the system. I only get "NaN". I understand that, this is often a
> result of imaginary components in the dynamical matrices, thus I've
> been redoing the calculations with different sets of parameters,
> however, to no avail.
>
> In scf I've been changing:
>
> 1. ecutwfc, and ecutrho (current values 80, and 650 Ry, respectively)
> 2. conv_thr (currently 1.0d-14)
> 3. k-point mesh (currently 36x36x1)
> 4. Pb pseudopotentials (currently Pb.rel-pbe-n-nc.UPF, previously
> Pb.rel-pbe-dn-rrkjus_psl.0.2.2.UPF)
> 5. Slab thickness (6-12 layers)
>
> In ph I've been testing:
>
> 1. tr2_ph (currently 1.0d-16, and up to 1.0d-17 with
> Pb.rel-pbe-dn-rrkjus_psl.0.2.2.UPF)
> 2. electron_phonon (interpolated, and simple)
> 3. q mesh (form 2x2x1 to 6x6x1)
>
> As a first step I've done the vc-relax, to relax the lattice constant
> of the slab. Next I perform relaxation with SOC included
> (etot_conv_thr, and forc_conv_thr= both 1.0d-6). Next I do the scf run
> e.g.:
>
> --------------------------------------------------------
> / &system//
> // ibrav= 4, //
> // a=3.503660834//
> // c=40//
> // nat= 6, ntyp= 1,//
> // ecutwfc =80.0,//
> // ecutrho = 650, //
> // occupations='smearing', smearing='mv', degauss=0.05//
> // lspinorb=.true., noncolin=.true.,
> starting_spin_angle=.true., starting_magnetization=0.0,//
> // la2F = .true.,//
> // nbnd = 48 //
> /////
> // &electrons//
> // mixing_mode = 'plain'//
> // mixing_beta = 0.5//
> // conv_thr = 1.0d-14//
> // ///
> // ATOMIC_SPECIES//
> // Pb 207.2 Pb.rel-pbe-n-nc.UPF//
> //ATOMIC_POSITIONS angstrom//
> //Pb 0.000000000 0.000000000 19.078230578//
> //Pb 0.000000000 0.000000000 27.596055131//
> //Pb 1.751830417 1.011419906 16.119173776//
> //Pb 1.751830417 1.011419906 24.874997245//
> //Pb 3.503661844 2.022839813 13.398232981//
> //Pb 3.503661844 2.022839813 21.915874849//
> //K_POINTS automatic//
> //36 36 1 0 0 0/
> --------------------------------------------------------
>
> this is followed by ph.x run:
>
> --------------------------------------------------------
> /&inputph//
> // outdir='Files/',//
> // prefix='QE'//
> // fildvscf='aldv',//
> // tr2_ph = 1.0d-16//
> // amass(1) = 207.2//
> // fildyn = 'Pb.dyn'//
> // alpha_mix=0.2//
> // electron_phonon='interpolated',//
> // el_ph_sigma=0.005, //
> // el_ph_nsigma=10,//
> // trans=.true.,//
> // ldisp=.true.//
> // nq1 = 6, nq2 = 6, nq3 = 1//
> // nogg = .true.//
> // asr = .true.//
> ////
> --------------------------------------------------------
>
> Next are q2r.x,
>
>
> --------------------------------------------------------
> /&input//
> // fildyn = 'Pb.dyn'//
> // zasr = 'crystal'//
> // flfrc = 'Pb.q661.fc'//
> // la2F=.true.//
> ////
> --------------------------------------------------------
>
> matdyn.x,
>
>
> --------------------------------------------------------
> /&input//
> // asr= 'simple'//
> // flfrc = 'Pb.q661.fc', flfrq='Pb.q661.freq', la2F=.true.,
> dos=.true.//
> // fldos='phonon.dos', nk1=60, nk2=60, nk3=1, ndos=50//
> // //
> --------------------------------------------------------
>
> and lambda.x
>
> --------------------------------------------------------
> /5 0.12 1 ! emax (something more than highest phonon mode in THz),
> degauss, smearing method //
> // 7//
> // 1 0.0000000 0.0000000 0.0000000 1.00//
> // 2 0.1666667 0.0962250 0.0000000 6.00//
> // 3 0.3333333 0.1924501 0.0000000 6.00//
> // 4 0.5000000 0.2886751 0.0000000 3.00//
> // 5 0.1666667 0.2886751 0.0000000 6.00//
> // 6 0.3333333 0.3849002 0.0000000 12.00//
> // 7 0.3333333 0.5773503 0.0000000 2.00//
> //elph_dir/elph.inp_lambda.1 //
> //elph_dir/elph.inp_lambda.2 //
> //elph_dir/elph.inp_lambda.3 //
> //elph_dir/elph.inp_lambda.4 //
> //elph_dir/elph.inp_lambda.5 //
> //elph_dir/elph.inp_lambda.6 //
> //elph_dir/elph.inp_lambda.7 //
> //0.10/
> --------------------------------------------------------
>
> The parameters I've used are relatively high in comparison to the Pb
> fcc example given by S. Poncé in 2018. Output of ph.x lacks negative
> frequencies, and DOS seems also fine:
>
> / # Frequency[cm^-1] DOS PDOS//
> // 0.0000000000E+00 0.0000000000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00//
> // 1.4306338313E+00 3.8122112950E-03 6.3283E-04 6.3953E-04
> 6.3336E-04 6.3251E-04 6.4093E-04 6.3306E-04//
> // 2.8612676626E+00 6.7934053704E-03 1.1376E-03 1.1328E-03
> 1.1244E-03 1.1215E-03 1.1385E-03 1.1386E-03//
> // 4.2919014939E+00 9.5022844921E-03 1.6112E-03 1.5734E-03
> 1.5628E-03 1.5658E-03 1.5730E-03 1.6162E-03//
> // 5.7225353252E+00 1.2941007092E-02 2.2167E-03 2.1293E-03
> 2.1167E-03 2.1337E-03 2.1145E-03 2.2302E-03
>
> //.../
>
> Also matdyn.x produces "lambda" file with:
>
> / Broadening 0.0050 lambda 1.7637 dos(Ef) 21.5379 omega_ln
> [K] 49.4388//
> // Broadening 0.0100 lambda 1.7028 dos(Ef) 21.2277 omega_ln
> [K] 49.7600//
> // Broadening 0.0150 lambda 1.6783 dos(Ef) 21.0885 omega_ln
> [K] 49.5935//
> // Broadening 0.0200 lambda 1.6881 dos(Ef) 21.1817 omega_ln
> [K] 49.4624//
> // Broadening 0.0250 lambda 1.7060 dos(Ef) 21.3799 omega_ln
> [K] 49.3380//
> // Broadening 0.0300 lambda 1.7218 dos(Ef) 21.5945 omega_ln
> [K] 49.1667//
> // Broadening 0.0350 lambda 1.7335 dos(Ef) 21.7888 omega_ln
> [K] 48.9500//
> // Broadening 0.0400 lambda 1.7414 dos(Ef) 21.9474 omega_ln
> [K] 48.7041//
> // Broadening 0.0450 lambda 1.7466 dos(Ef) 22.0647 omega_ln
> [K] 48.4423//
> // Broadening 0.0500 lambda 1.7499 dos(Ef) 22.1428 omega_ln
> [K] 48.1738/
>
> so shouldn't Tc be just a product of substitution into McMillan
> formula using values of omega_ln and lambda?
>
> Regards,
> Maciej Szary//
> //
> --
> Research Assistant,
> Institute of Physics,
> Poznan University of Technology
> Piotrowo 3A, 61-138 Poznan
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