[QE-users] Potential issue with charge density cutoff convergence and K-point grid convergence

[Martina Lessio]

Dear Quantum Espresso community,

I am new to Quantum Espresso and I am trying to run some simple simulations
on MoTe2 bulk. Unfortunately I seem to be having some issues with some
preliminary convergence tests for charge density cutoff and K-point grid
and I am hoping to get some help from you on this.
Here is a graph with the results of the charge density cutoff convergence
test I performed while setting the kinetic energy cutoff equal to 60 Ry (I
performed a test to set this as well):

I am worried about these results because I would expect the total energy to
go down rather than going up when I increase ecutrho. I also observe a
similar energy trend when I increase the k-point grid, which also seems
unusual and possibly wrong to me.
I am copying below the input I have used for these calculations and I would
greatly appreciate any help with figuring our whether I am doing something
wrong.

Thank you so much!

Kind Regards,
Martina Lessio

Postdoctoral Research Scientist
Department of Chemistry
Columbia University

 &control

    calculation = 'scf'

    restart_mode='from_scratch',

    prefix='MoTe2_ecutwfc',

    pseudo_dir = '/home/mlessio/espresso-5.4.0/pseudo/',

    outdir='/home/mlessio/espresso-5.4.0/tempdir/'

 /

 &system

    ibrav= 4, A=3.530, B=3.530, C=13.882, cosAB=-0.5, cosAC=0, cosBC=0,

    nat= 6, ntyp= 2,

    ecutwfc =60.0 ecutrho=300.

    nspin =4, lspinorb =.true., noncolin=.true.

 /

 &electrons

    mixing_mode = 'plain'

    mixing_beta = 0.7

    conv_thr =  1.0d-8

 /

ATOMIC_SPECIES

 Mo  95.96 Mo.rel-pbe-spn-rrkjus_psl.1.0.0.UPF

 Te  127.6 Te.rel-pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS {crystal}

Te     0.333333334         0.666666643         0.625000034

Te     0.666666641         0.333333282         0.375000000

Te     0.666666641         0.333333282         0.125000000

Te     0.333333334         0.666666643         0.874999966

Mo     0.333333334         0.666666643         0.250000000

Mo     0.666666641         0.333333282         0.750000000


K_POINTS {automatic}

  8 8 2 0 0 0
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