# Error: "two consecutive points in the path which are equal" during band structure calculations

**URL:** <https://discourse.abinit.org/t/error-two-consecutive-points-in-the-path-which-are-equal-during-band-structure-calculations/3299>\
**Category:** Ground state\
**Created:** [April 8, 2023, 2:01pm UTC](https://discourse.abinit.org/t/error-two-consecutive-points-in-the-path-which-are-equal-during-band-structure-calculations/3299 "2023-04-08T14:01:06Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![FSPlum](https://discourse.abinit.org/letter_avatar_proxy/v4/letter/f/9e8a1a/32.png) [@FSPlum](https://discourse.abinit.org/u/FSPlum)\
**Post date:** [April 8, 2023, 2:01pm UTC](https://discourse.abinit.org/t/error-two-consecutive-points-in-the-path-which-are-equal-during-band-structure-calculations/3299/1 "2023-04-08T14:01:06Z")

</div>

Hi! I’m rather new to abinit. I would like to calculate the band structure of an aluminium silicate mineral (microcline) using abinit following tutorial 3.5, which I modified slightly to use it for microcline. I ran a convergence study on ecut and also for my k point grid. I have performed a geometry optimisation and now use the new values for acell, rprim and xred for the band structure calculation. I also use the defined k grid. However, when I run the code to calculate the band structure I always receive the followin error message:

— !ERROR  
src\_file: m\_kpts.F90  
src\_line: 3044  
mpi\_rank: 0  
message: |  
found two consecutive points in the path which are equal  
This is not allowed, please modify the path in your input file  
…

I tried some trouble shooting. Tutorial 3.5 runs without problems, when I don’t modify anything. I also ran the first part of the band structure calculation, which is the usual self-consistent calculation, and this also works. However, when I put both things together. I always receive the error message. I think it has something to do with my k points, but I really have no idea anymore how to make it work.  
I’d be really grateful, if you could help me with this. I copy the code in at the bottom of the post.

Thank you very much.  
Best wishes,  
Svenja

```auto
# Crystalline microcline: computation of the band structure
#
# First, a SCF density computation, then a non-SCF band structure calculation.

ndtset 2

#Definition of the unit cell
acell 1.4431635953E+01 1.5028696742E+01 1.3713958625E+01 Bohr
# acell and rprim values from Geometry Optimisation II are used (TestMicrocline_230321-1)
rprim 5.2707510634E-01 -8.4981857575E-01 4.6966109111E-04
           5.7496495356E-01 8.1817797099E-01 -3.3161944231E-04
          -4.3589715791E-01 5.7621885097E-03 8.9997803579E-01

#Definition of the atom types
ntypat 4 # There are four types of atoms K Al Si O
znucl 19 13 14 8 # The keyword "znucl" refers to the atomic number of the
                  # possible type(s) of atom. The pseudopotential(s)
                  # mentioned in the "files" file must correspond
                  # to the type(s) of atom. Here, the only type is Silicon.
pp_dirpath "/usr/local/Cellar/abinit/9.6.2/share/tests/tutorial/Input/TestMicrocline" # This is the path to the directory where
                                # pseudopotentials for tests are stored
pseudos "K_PBEsol.psp8, Al_PBEsol.psp8, Si_PBEsol.psp8, O_PBEsol.psp8"
                                # Name and location of the pseudopotential

#Definition of the atoms
natom 26 # There are 26 atoms
typat 1 1 2 2 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4
xred # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom

                  2.8962262313E-01 2.7073432893E-01 1.3588122589E-01
                  7.1037737687E-01 7.2926567107E-01 8.6411877411E-01
                  8.2353464312E-01 1.9845918241E-01 2.1759185164E-01
                  1.7646535688E-01 8.0154081759E-01 7.8240814836E-01
                  1.9013592856E-01 8.3117386529E-01 2.3269927132E-01
                  8.0986407144E-01 1.6882613471E-01 7.6730072868E-01
                  5.9027151657E-01 8.3093518887E-01 3.4054626986E-01
                  4.0972848343E-01 1.6906481113E-01 6.5945373014E-01
                  8.1900055860E-01 5.9105087426E-01 3.5139250876E-01
                  1.8099944140E-01 4.0894912574E-01 6.4860749124E-01
                  8.5635777530E-01 1.4321089883E-01 9.8273125768E-01
                  1.4364222470E-01 8.5678910117E-01 1.7268742321E-02
                  6.2677113864E-01 6.3872676248E-01 2.8565363024E-01
                  3.7322886136E-01 3.6127323752E-01 7.1434636976E-01
                  6.7516628833E-01 9.6804156618E-01 2.2066494137E-01
                  3.2483371167E-01 3.1958433823E-02 7.7933505863E-01
                  9.7318882382E-01 6.9143075804E-01 2.4098357768E-01
                  2.6811176182E-02 3.0856924196E-01 7.5901642232E-01
                  7.1416021432E-01 3.5421960524E-01 2.5096626849E-01
                  2.8583978568E-01 6.4578039476E-01 7.4903373151E-01
                  3.4124364979E-01 7.3394394327E-01 2.7081652469E-01
                  6.5875635021E-01 2.6605605673E-01 7.2918347531E-01
                  7.0461970951E-02 3.1459781488E-01 4.0398949326E-01
                  9.2953802905E-01 6.8540218512E-01 5.9601050674E-01
                  3.0215256539E-01 5.2472747028E-02 4.1086804869E-01
                  6.9784743461E-01 9.4752725297E-01 5.8913195131E-01
                  # for xred values from Geometry Optimisation II are used (TestMicrocline_230321-1)

#Definition of the planewave basis set
ecut 40 # Maximal kinetic energy cut-off, in Hartree

#Definition of the SCF procedure
nstep 20 # Maximal number of SCF cycles
diemac 12.0 # Although this is not mandatory, it is worth to
                  # precondition the SCF cycle. The model dielectric
                  # function used as the standard preconditioner
                  # is described in the "dielng" input variable section.
                  # Here, we follow the prescription for bulk silicon.

# Dataset 1 : usual self-consistent calculation
# Here I have now inserted the results for the k grid, I got previously,
#so the following bit is changed from the original Tutorial 3.5
#Definition of the k-point grid
kptopt1 1 # Option for the automatic generation of k points, taking
                  # into account the symmetry
prtkpt 1 # generates a suitable k-point grid
kptrlatt1 0 2 2
          2 0 2
          2 2 0 # results from k point grid test #38
nshiftk1 1 # default
                   # repeated four times, with different shifts :
shiftk1 0 0 0 # default shiftk 0.5 0.5 0.5
# The two following lines are from tutorial 3.5
prtden1 1 # Print the density, for use by dataset 2
toldfe1 1.0d-6 # This value is way too large for most realistic studies of materials

# Dataset 2 : the band structure
iscf2 -2
getden2 -1
kptopt2 -3 # will have three segments in the band structure
nband2 8
ndivsm2 10 # 10 divisions of the smallest of the 3 segments, delimited
                       # by the 4 points defined by kptbounds.
kptbounds2 0.5 0.5 0.0 # L point
            0.0 0.0 0.0 # Gamma point
            0.0 0.0 0.0 # X point
            1.0 1.0 1.0 # Gamma point in another cell.
            # the values for the Brouillon zone are taken from my spreadsheet for triclinic systems
tolwfr2 1.0d-12
enunit2 1 # Will output the eigenenergies in eV

##############################################################
# This section is used only for regression testing of ABINIT #
##############################################################
#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test =
#%% TestMicrocline_230408-1.abo, tolnlines= 0, tolabs= 0.000e+00, tolrel= 0.000e+00
#%% [paral_info]
#%% max_nprocs = 4
#%% [extra_info]
#%% authors = Unknown
#%% keywords =
#%% description = Crystalline feldspar: computation of band structure
#%%<END TEST_INFO>

```

---

<div class="post-metadata">

**Author:** ![jzwanzig](https://discourse.abinit.org/letter_avatar_proxy/v4/letter/j/cdc98d/32.png) [@jzwanzig](https://discourse.abinit.org/u/jzwanzig)\
**Post date:** [April 8, 2023, 2:25pm UTC](https://discourse.abinit.org/t/error-two-consecutive-points-in-the-path-which-are-equal-during-band-structure-calculations/3299/2 "2023-04-08T14:25:25Z")

</div>

Hi–  
in your input file for kptbounds2, you have 4 points, but you have defined points 2 and 3 to be identical (0 0 0 for Gamma, but you also have 0 0 0 for # X). That’s why it says you have overlapping k pts.

Also, your tolerance for the convergence in the first data set is too low for realistic convergence, I’d change the toldfe1 value to something like tolvrs1 1.0D-12 (it’s the potential and density that you really want converged here, more so than the energy).

---

<div class="post-metadata">

**Author:** ![FSPlum](https://discourse.abinit.org/letter_avatar_proxy/v4/letter/f/9e8a1a/32.png) [@FSPlum](https://discourse.abinit.org/u/FSPlum)\
**Post date:** [April 9, 2023, 7:39am UTC](https://discourse.abinit.org/t/error-two-consecutive-points-in-the-path-which-are-equal-during-band-structure-calculations/3299/3 "2023-04-09T07:39:20Z")

</div>

Thank you for your help! That worked.

---

<div class="post-metadata">

**Author:** ![gingras.ol](https://discourse.abinit.org/user_avatar/discourse.abinit.org/gingras.ol/32/275_2.png) [@gingras.ol](https://discourse.abinit.org/u/gingras.ol)\
**Post date:** [April 11, 2023, 5:25pm UTC](https://discourse.abinit.org/t/error-two-consecutive-points-in-the-path-which-are-equal-during-band-structure-calculations/3299/4 "2023-04-11T17:25:32Z")

</div>