ABINIT Discussion Forums

So, I have a structure which has coordinates that are not on high symmetry points. Wyckoff positions for the space group in question show multipliers of (0,0,0) + (2/3,1/3,1/3) + (1/3,2/3,2/3) + Let's say this is for space group 166 For the purposes of this post: I have an atomic position for an ato...

I am trying to assign the correct amount of time to my phonon calc. Here is an example: I have a very low symmetry 20 atom unit cell. I am going to specify rfatpol 1 20 How many iterations of the 2nd deriv energies will there be? 3n+3? or more? I ask this because I did a calc w/ 20 atoms, knew it wo...

I am stumped on what to do about the following: 1. I relax a structure of say 20 atoms to < 1x10-6 Ha/bohr (tolmxf 1.0d-6) 2. I use this relaxed structures acell and xred as inputs to the beginning of a phonon calculation that has tolvrs 10d-18 . 3. when I get the forces back after the completion of...

Whe I do a polarization calc, I get numbers that don't seem to add up: Polarization in cartesian coordinates (C/m^2): (the sum of the electronic and ionic Berry phase has been fold into [-1, 1]) Electronic berry phase: 0.183E+00 -0.155E-17 0.215E+00 Ionic: -0.157E+00 0.737E-15 -0.196E+00 Total: -0.1...

Thanks, Professor.
I reviewed the ABinit input vars and, using the same script as before, included rfasr 2
and it worked like a charm eliminating the negative phonons and a small positive one as well.

I have heard, but am not sure, that when doing a GAMMA phonon calculation, sometimes seeing small negative phonons w/ frequencies no less than -20 cm-1 are really not "there"; that they really are an artifact of the calculation. Is this true? And if true, what is a good cut off frequency t...

Many times my script hangs after reaching the convergence criteria and the logfile indicates that wavefunction file is trying to be written.... but nothing more happens after that (for hours). Is there any way to turn the writing of the wavefunctions off?

I think there has been a misunderstanding here: Though abinit labels iterations with ETOT, for structure convergence I thought ETOT meant etotal and the log file labels it as such. The ETOT iterations I describe earlier seem to have a column heading of 2nd derivative of energy, as I'd expect from th...

I should add that it is not really ETOT that is being converged, but the 2nd derivative of the energy

I am using LDA based PSPs created using the Opium software and they are termed norm-conserving, designed non-local with 25 Ha cutoff in energy for the plane waves. Thus, my ecut in ABINIT is limited to a maximum 25 Ha as well. So, my change from iscf 3 (Anderson mixing) to iscf 5 (Congruent Gradient...

I can think of one idea, but not sure why it would/would not help: changing iscf from anderson mixing to CG method.

Hi, I am investigating a real material according to entries in the ICSD database: hexagonal P63mmc BaTiS3. However, my phonon calculation "explodes" --- the ETOT during several iterations starts off looking for a minimum, and then grows to >1.0x10E18. I believe I have followed best practic...

Hi, I have read this forum extensively, but am still striking out on some of my phonon calculations. I have a structure which relaxes to a metal. My relaxation conditions are toldfe 1x10-12 and tolmxf 1x10-6. I use occopt 7 and tsmear of 0.005. I then attempt a resp. fn run using tolvrs 1.0-22. I co...

I have an insulator, PbTiO3. I set it up two ways: in a cubic fashion and a tetragonal fashion. I have pseudopotential in which there are 14 val. electrons for Pb, 12 for Ti, and 6 for O. So, in my 5 atom unit cell I have 44 electrons. since this is an insulator, I need 22 bands. Ok, so far. So, pla...

I pulled the following info from ICSD: PbO sp group P4/nmm S (129) Pb is in wyckoff pos 2c (0.25 0.25 0.2385); O is in wyckoff pos. 2a (0.75 0.25 0 I plug the info into ABINIT and run.... but the job fails as I am told: Largest error (above) is so large (0.01) that either input atomic coordinates (x...

Unfortunately, I am testing a non-existent tertiary compound locked into place artificially by using spgroup.
So, I have nothing to compare it against.

I changed the input file over the weekend as I too saw my error in setting up my ntypat. And, I mis-wrote that I used a shift of 111 -- 0.5 0.5 0.5 was used. So: my only problem remaining is that the nkpt are different between different parts of the run. Do the variables and params you suggested in ...

when calculating the frozen phonon at gamma for a metal, what should the occopt and tsmear be set to?
thanks,
JB

So, I am having at least 2 problems. Problem 1: I have placed BaTiO3 in the r3m space group. My PSP electrons are for Ba: 10; Ti: 12; and O: 6 for a total of 40. I know from previous calcs that BaTiO3 in this space group is calculated as an insulator. Yet, when I use nband = 20 (or even add a few mo...

thanks for your response. I should have been more explicit: It is simple enough to determine the number of bands needed for a ph. calc (or any calc) for an insulator: add up all the electrons specified by the pseudoptentials and divide by 2. What is acceptable for a metal? QE automatically adds 20% ...

Your tutorial example, AlAs, is for an insulator. "This lesson aims at showing how to get the following physical properties, for an insulator ..."
What needs to be done, changed, or accounted for if I want to do a metalllic compound?
Can you supply an example?
Thanks,
JB

Hi.

I see that Lesson 3.5 of the tutorial gives values for variables for the electronic band structure of an insulator.

Is there anything different I have to do for a metal?

Hi, So I ran a relaxation calculation with the xred in the P63/mmc (#194) space group and forced abinit to find a sol'n within this space group by using the spgroup variable and setting it equal to 194. this calc returns xred in the 194 group. fine so far. Now, 194 is a hexagonal space group. so, I ...

I am not looking for a ground state though... for example: I would like to see how a NaCl BCC energy compares to a NaCL FCC ground state. Now, this is an easy state as none of the coords are on decimal sites.... but a lot of xray diffraction results show atoms to be on decimal sites. So, for another...

Hi everyone: maybe I just am not understanding the abinit input variables involving space groups. Here is my question: How do I perform a relaxation that maintains a particular space group throughout? say I input starting coords that are for space group 63. How do I keep abinit only searching within...