[QE-users] oscillations in G(V) diagrams

[Jakob Kraus]

Dear QE users,


I am trying to calculate heat capacities, and to this end, I have 
calculated the Gibbs energy as a function of volume

at several temperatures in a range of 0-700 K.

However, the functions that result from this do not show a single 
minimum, but rather a whole lot of oscillations, which

seem to originate from the phonons, since the E(V) diagram at 0 K shows 
a single minimum as expected.

I am thankful for any help you can offer with getting rid of these 
oscillations.

I have attached input files and some plots to showcase the problem.


Best regards,


Jakob Kraus, TU Freiberg
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&input
fildyn  =   'matdyn'
zasr    =   'crystal'
flfrc   =   'force.fc'
/
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&CONTROL
   calculation      = 'scf'
   title            = 'Zr_BH4_4_v95'
   verbosity        = 'high'
   restart_mode     = 'from_scratch'
   tstress          = .true.
   tprnfor          = .true.
   outdir           = './'
   prefix           = 'espresso'
   pseudo_dir       = '/home/kraus/pslibrary_pp/PBE_PAW'
/
&SYSTEM
   ibrav            = 1
   ecutwfc          = 120
   ecutrho          = 960
   occupations      = 'fixed'
   nspin            = 1
   ntyp             = 3
   nat              = 21
   celldm(1)        = 11.718963054402725
/
&ELECTRONS
   electron_maxstep = 300
   conv_thr         = 1e-10
   mixing_beta      = 0.7
/

ATOMIC_SPECIES
Zr 91.224 Zr.pbe-spn-kjpaw_psl.1.0.0.UPF
B 10.81 B.pbe-n-kjpaw_psl.1.0.0.UPF
H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF

K_POINTS automatic
2 2 2  0 0 0

ATOMIC_POSITIONS angstrom
Zr 3.1007040770 3.1007040770 3.1007040770 
B 4.4131080846 1.7883000693 1.7883000693 
B 1.7883000693 4.4131080846 1.7883000693 
B 1.7883000693 1.7883000693 4.4131080846 
B 4.4131080846 4.4131080846 4.4131080846 
H 3.2091046915 1.6105056976 1.6105056976 
H 2.9923034624 4.5909024564 1.6105056976 
H 2.9923034624 1.6105056976 4.5909024564 
H 3.2091046915 4.5909024564 4.5909024564 
H 1.6105056976 3.2091046915 1.6105056976 
H 1.6105056976 2.9923034624 4.5909024564 
H 4.5909024564 2.9923034624 1.6105056976 
H 4.5909024564 3.2091046915 4.5909024564 
H 1.6105056976 1.6105056976 3.2091046915 
H 4.5909024564 1.6105056976 2.9923034624 
H 1.6105056976 4.5909024564 2.9923034624 
H 4.5909024564 4.5909024564 3.2091046915 
H 5.0910460240 1.1103621300 1.1103621300 
H 1.1103621300 5.0910460240 1.1103621300 
H 1.1103621300 1.1103621300 5.0910460240 
H 5.0910460240 5.0910460240 5.0910460240 

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phdos Zr_BH4_4
&INPUTPH
    tr2_ph      =   1.D-14
    prefix      =   'espresso'
    outdir      =   './'
    fildyn      =   'matdyn'
    ldisp       =   .true.
    nq1         =   3
    nq2         =   3
    nq3         =   3
/
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&input
    asr     =   'crystal'
    flfrc   =   'force.fc'
    dos     =   .true.
    fldos   =   'matdyn.dos'    
    deltaE  =   1
    nk1     =   20
    nk2     =   20
    nk3     =   20
/