Dear Caterina, thank you for your attention.

At first, I performed a ground state calculation, then using EFERMI.OUT and STATE.OUT, run a TDDFT with the attached input.xml.
After the end of tddft, I used the script in the exciting website to convert outputs for xmgrace files. Xmgrace shown a line like f(x)=x. In the below, I bring the lossfunction_Loss.agr:

0.000000000 1.898329327e-28
0.3023487096E-01 1.096377288e-21
0.6046974191E-01 2.192754361e-21
0.9070461287E-01 3.289131443e-21
0.1209394838 4.385508533e-21
0.1511743548 5.48188563e-21
0.1814092257 6.578262719e-21
0.2116440967 7.674639813e-21
0.2418789676 8.771016906e-21
0.2721138386 9.867393996e-21
0.3023487096 1.096377109e-20
0.3325835805 1.20601482e-20
0.3628184515 1.315652529e-20
0.3930533224 1.425290239e-20
0.4232881934 1.53492795e-20
0.4535230643 1.644565661e-20
0.4837579353 1.754203373e-20
0.5139928062 1.863841084e-20
0.5442276772 1.973478796e-20
0.5744625482 2.083116509e-20
0.6046974191 2.192754221e-20
0.6349322901 2.302391935e-20
0.6651671610 2.412029647e-20
0.6954020320 2.521667363e-20
0.7256369029 2.631305078e-20
0.7558717739 2.740942793e-20
0.7861066448 2.850580509e-20
0.8163415158 2.960218224e-20
0.8465763868 3.069855941e-20
0.8768112577 3.179493658e-20
0.9070461287 3.289131377e-20
0.9372809996 3.398769095e-20
0.9675158706 3.508406816e-20
0.9977507415 3.618044534e-20
1.027985612 3.727682256e-20
1.058220483 3.837319977e-20
1.088455354 3.9469577e-20
1.118690225 4.056595423e-20
1.148925096 4.166233147e-20
1.179159967 4.275870871e-20
1.209394838 4.385508596e-20
1.239629709 4.495146323e-20
1.269864580 4.604784051e-20
1.300099451 4.714421778e-20
1.330334322 4.824059508e-20
1.360569193 4.933697237e-20
1.390804064 5.043334969e-20
1.421038935 5.152972701e-20
1.451273806 5.262610435e-20
1.481508677 5.372248169e-20
1.511743548 5.481885904e-20
1.541978419 5.59152364e-20
1.572213290 5.701161377e-20
1.602448161 5.810799116e-20
1.632683032 5.920436855e-20
1.662917903 6.030074596e-20
1.693152774 6.139712338e-20
1.723387644 6.249350081e-20
1.753622515 6.358987825e-20
1.783857386 6.468625571e-20
1.814092257 6.578263319e-20
1.844327128 6.687901067e-20
1.874561999 6.797538816e-20
1.904796870 6.907176568e-20
1.935031741 7.01681432e-20
1.965266612 7.126452073e-20
1.995501483 7.236089829e-20
2.025736354 7.345727586e-20
2.055971225 7.455365343e-20
2.086206096 7.565003103e-20
2.116440967 7.674640863e-20
2.146675838 7.784278626e-20
2.176910709 7.89391639e-20
2.207145580 8.003554155e-20
2.237380451 8.113191921e-20
2.267615322 8.222829691e-20
2.297850193 8.332467461e-20
2.328085064 8.442105233e-20
2.358319935 8.551743006e-20
2.388554805 8.661380782e-20
2.418789676 8.77101856e-20
2.449024547 8.880656338e-20
2.479259418 8.990294118e-20
2.509494289 9.0999319e-20
2.539729160 9.209569684e-20
2.569964031 9.31920747e-20
2.600198902 9.428845259e-20
2.630433773 9.538483047e-20
2.660668644 9.648120839e-20
2.690903515 9.757758633e-20
2.721138386 9.867396427e-20
2.751373257 9.977034225e-20
2.781608128 1.008667202e-19
2.811842999 1.019630983e-19
2.842077870 1.030594763e-19
2.872312741 1.041558543e-19
2.902547612 1.052522324e-19
2.932782483 1.063486105e-19
2.963017354 1.074449886e-19
2.993252225 1.085413668e-19
3.023487096 1.096377449e-19
3.053721967 1.107341231e-19
3.083956837 1.118305013e-19
3.114191708 1.129268795e-19
3.144426579 1.140232578e-19
3.174661450 1.15119636e-19
3.204896321 1.162160143e-19
3.235131192 1.173123926e-19
3.265366063 1.18408771e-19
3.295600934 1.195051493e-19
3.325835805 1.206015277e-19
3.356070676 1.216979061e-19
3.386305547 1.227942846e-19
3.416540418 1.23890663e-19
3.446775289 1.249870415e-19
3.477010160 1.2608342e-19
3.507245031 1.271797985e-19
3.537479902 1.282761771e-19
3.567714773 1.293725557e-19
3.597949644 1.304689343e-19
3.628184515 1.315653129e-19
3.658419386 1.326616915e-19
3.688654257 1.337580702e-19
3.718889128 1.348544489e-19
3.749123998 1.359508277e-19
3.779358869 1.370472064e-19
3.809593740 1.381435852e-19
3.839828611 1.39239964e-19
3.870063482 1.403363429e-19
3.900298353 1.414327218e-19
3.930533224 1.425291007e-19
3.960768095 1.436254796e-19
3.991002966 1.447218585e-19
4.021237837 1.458182375e-19
4.051472708 1.469146165e-19
4.081707579 1.480109956e-19
4.111942450 1.491073747e-19
4.142177321 1.502037538e-19
4.172412192 1.513001329e-19
4.202647063 1.523965121e-19
4.232881934 1.534928912e-19
4.263116805 1.545892705e-19
4.293351676 1.556856497e-19
4.323586547 1.56782029e-19
4.353821418 1.578784083e-19
4.384056289 1.589747877e-19
4.414291160 1.60071167e-19
4.444526030 1.611675464e-19
4.474760901 1.622639259e-19
4.504995772 1.633603053e-19
4.535230643 1.644566848e-19
4.565465514 1.655530644e-19
4.595700385 1.66649444e-19
4.625935256 1.677458235e-19
4.656170127 1.688422032e-19
4.686404998 1.699385828e-19
4.716639869 1.710349626e-19
4.746874740 1.721313423e-19
4.777109611 1.732277221e-19
4.807344482 1.743241019e-19
4.837579353 1.754204817e-19
4.867814224 1.765168616e-19
4.898049095 1.776132415e-19
4.928283966 1.787096214e-19
4.958518837 1.798060014e-19
4.988753708 1.809023814e-19
5.018988579 1.819987615e-19
5.049223450 1.830951415e-19
5.079458321 1.841915217e-19
5.109693191 1.852879018e-19
5.139928062 1.86384282e-19
5.170162933 1.874806622e-19
5.200397804 1.885770425e-19
5.230632675 1.896734228e-19
5.260867546 1.907698031e-19
5.291102417 1.918661835e-19
5.321337288 1.929625639e-19
5.351572159 1.940589444e-19
5.381807030 1.951553249e-19
5.412041901 1.962517054e-19
5.442276772 1.97348086e-19
5.472511643 1.984444666e-19
5.502746514 1.995408472e-19
5.532981385 2.006372279e-19
5.563216256 2.017336087e-19
5.593451127 2.028299894e-19
5.623685998 2.039263702e-19
5.653920869 2.050227511e-19
5.684155740 2.06119132e-19
5.714390611 2.072155129e-19
5.744625482 2.083118939e-19
5.774860353 2.094082749e-19
5.805095223 2.105046559e-19
5.835330094 2.11601037e-19
5.865564965 2.126974182e-19
5.895799836 2.137937993e-19
5.926034707 2.148901805e-19
5.956269578 2.159865618e-19
5.986504449 2.170829431e-19
6.016739320 2.181793245e-19
6.046974191 2.192757059e-19
6.077209062 2.203720873e-19
6.107443933 2.214684688e-19
6.137678804 2.225648503e-19
6.167913675 2.236612318e-19
6.198148546 2.247576134e-19
6.228383417 2.258539951e-19
6.258618288 2.269503768e-19
6.288853159 2.280467585e-19
6.319088030 2.291431403e-19
6.349322901 2.302395222e-19
6.379557772 2.31335904e-19
6.409792643 2.32432286e-19
6.440027514 2.335286679e-19
6.470262384 2.346250499e-19
6.500497255 2.35721432e-19
6.530732126 2.368178141e-19
6.560966997 2.379141963e-19
6.591201868 2.390105785e-19
6.621436739 2.401069607e-19
.
.
.
… up to 50 eV increase linearly.

Epsilon file is like to loss function (linear).

Please help me and guide me for what is wrong?

Dear Hajar,

rather than a f(x)=x curve, your output file seems to be zero everywhere.
Before using the script for xmgrace, I suggest you to give a look at the output file generated by exciting, which in your case is LOSS_*.OUT. If the second column of this file is also zero (or some number xxxe-19), than there is something wrong with your calculation.
The input file that you attached in your first post seems correct at a quick glance. What about the ground state calculation? Did it converge? Did you check the output files?

Regards,

Caterina Cocchi
(exciting team)

Dear Caterina,
Yes, LOSS_FXCALDA_OC11_QMT001.OUT is near zero, too. Also, Epsilon_*.OUT is like the LOSS_*.OUT!
input.xml for ground state is:
<input>

<title>BN0.5P0.5 P-4m2</title>

<structure speciespath="/opt/exciting-ber/species">

<crystal>
<basevect>5.626901 0.0 0.0</basevect>
<basevect>0.0 5.626901 0.0</basevect>
<basevect>0.0 0.0 7.957640</basevect>
</crystal>

<species speciesfile="B.xml" rmt="1.1">
<atom coord="0.00 0.50 0.75"/>
<atom coord="0.50 0.00 0.25"/>
</species>
<species speciesfile="N.xml" rmt="1.6">
<atom coord="0.00 0.00 0.00"/>
</species>
<species speciesfile="P.xml" rmt="1.6">
<atom coord="0.50 0.50 0.50"/>
</species>

</structure>

<groundstate
ngridk="8 8 6"
xctype="GGA_PBE"
gmaxvr="14">
</groundstate>

</input>

and it converged successfully (in both lithium and beryllium versions) as shown in the INFO.OUT. But in both version, BSE and TDDFT give me LOSS_ and EPSILON_*.OUT near zero like above!

Can you perform my case in both ground state and BSE calculations with my input file and see your results, Please?!
I don't know what is wrong really!
It is necessary to say: I'm calculating optical properties of BN, BN0.75P0.25, BN0.5P0.5, BN0.25P0.75 and BP within BSE and TDDFT. I performed BN, BP and BN0.25P0.75 successfully, but BN0.5P0.5 and BN0.75P0.25 's outputs are near zero, like above.( I have already optimized all structures and have calculated optical properties in RPA with Wien2k code).

Thank you very very much for your attention and your kindness.
Best Wishes
Hajar

Dear Caterina

when bse is running, it is wrote in the output file: "There is no KS-gap present", while the band gap of the BN0.5P0.5 is 0.388 eV with GGA_PBE.

Also, in the WARNING.OUT is:

Warning(occupy): smallest valence eigenvalue less thanminimum linearization energy : -64.58481383 -0.6020000000
for s.c. loop 1

Warning(occupy): smallest valence eigenvalue less thanminimum linearization energy : -228413.6947 -0.6020000000
for s.c. loop 2

Warning(charge): total charge density incorrect for s.c. loop 2
Calculated : 32.35806089
Required : 32.00000000

Can it be the reason of zero output of BSE? (there is no such error or warning for TDDFT)
What is the mean of these warnings?
Please guide me
Thank you so much
Hajar

Dear Hajar,

the warning message you obtain from the BSE calculation indicates that your system is metallic and therefore no optical absorption occurs. As I explained in a previous post, the presence of a gap in the ground state is not itself an indication of the presence of an optical gap, which is the one that enters into play in an excited state calculation.

In my opinion the problem you are experiencing resides in the ground state calculation, which I warmly suggest you to check carefully.
The eigenvalues that appear in your warning message look quite weird. Especially the second one: -228413.6947 Ha does not seem to be a physical number.
Are you sure that your ground state calculation is converged with respect to all the significant parameters (lattice parameter, rgkmax, k-point mesh etc)? Did you compare your outcomes from the ground state (i.e. density of states, band structure) with the literature?

Regards,

Caterina Cocchi
(exciting team)

Dear Caterina
Thank you so much.
By attention to your opinion, I re-performed my ground state again but with xctype="LSDAPerdew-Wang" (for the probebly better calculation of gap). With this option, I got physical output files for EPSILON_ and LOSS_*.OUT.

Thank you very very much because of your guidance and your kindness.
Best Regards
Hajar