ABINIT Discussion Forums

Dear Andy, How can I check the vibration of the unstable mode and the forces of the atoms? Just for clarification- I realized that originally both NbB2 and TaB2 had negative frequencies, but the paper said that both were positive. Transitioning from GGA-PBE to LDA helped NbB2 become positive, but Ta...

Dear Andy, Thanks for your reply! I redid the relaxation with the variable pawxcdev, but this actually seemed to make the negative frequency worse with the GGA-PBE... With the new relaxation, I got the negative frequencies with the first and last q-points (0.00000000E+00 0.00000000E+00 0.00000000E+0...

Dear Eric, Thanks for your reply! I have returned the phonon frequencies for the GGA-PBE pseudopotential (with the negative). Here are the frequencies with asr=0 Phonon frequencies in cm-1 : - 1.258512E+02 1.689430E+02 1.940943E+02 3.377814E+02 4.090744E+02 - 4.166469E+02 7.080554E+02 8.230405E+02 8...

Dear Andy and Eric, Thank you for your responses! I used the grep command and got the following: Phonon frequencies in cm-1 : - 5.171502E+00 5.171502E+00 1.165883E+01 3.042359E+02 3.042359E+02 - 3.651107E+02 5.250094E+02 8.804881E+02 8.804881E+02 -- Phonon frequencies in cm-1 : - 3.260848E+01 8.0615...

Dear Eric, Thank you for the response and explanation! Part of my groundstate output file for dataset 3 says ==> Compute Derivative Database <== 2nd-order matrix (non-cartesian coordinates, masses not included, asr not included ) j1 j2 matrix element dir pert dir pert real part imaginary part 1 1 1 ...

Dear Andy, Thank you for answering! I tested my anaddb file with different values of rifcsph, and rifcsph=8 helped the negative frequency disappear at the K point. However, small negative frequencies do appear at the gamma point. How do I determine which value of rifcsph I should use/perform converg...

Dear Eric, Thank you for your reply! I did check with a larger number of nbands (27), and the imaginary frequency was still there. You mentioned: - do you have the instability in the DFPT calculations or is it restricted in points between the DFPT calcaulted q-points? Could you please elaborate on h...

Dear abinit users, I am trying to calculate the phonon frequency for monolayer TaB2, which has entirely positive values in the paper "Predicting Novel 2D MB2 (M=Ti, Hf, V, Nb, Ta) Monolayers with Ultrafast Dirac Transport Channel and Electron-orbital Controlled Negative Poisson’s Ratio." My calculat...

Dear abinit users, I am trying to calculate the Tc of PbTaSe2, which is experimentally around 3.8K. But, when I try to calculate it, my value is nearly ten times smaller! Here is my groundstate input file and anaddb file. Any help is greatly appreciated! ndtset 32 pawxcdev 0 # # DATASET 1 : make gro...

Hi, I am a relatively new user of Abinit. I am having some trouble with the V3Si cubic structure. Starting with the experimental lattice constants, I first relaxed the structure to find the optimized lattice constants, and it was able to converge. I plotted the structure using Xcrysden and it seemed...