dear all

l use VCA mehtod to compute the elastic and piezoelectic constant of PZT as the tutorial indicated.In the second step, l find some warning.

1.Alchemical pseudopotential with nlcc!

2. Density went too small (lower than xc_denpos) at 27629 points

and was set to xc_denpos = 1.00E-14. Lowest was -0.34E+02.

Likely due to too low boxcut or too low ecut for pseudopotential core charge.

3. Alchemical crystals are not fully supported by the netcdf format

Important parameters (e.g. znucl, symbols) are not written with the correct value

4.input nkpt=256 not equal disk file nkpt=160

5. input kptopt= 2 /= disk file kptopt= 1

6.Restart of self-consistent calculation need translated wavefunctions.

7.nstep 60 was not enough SCF cycles to converge.

8. WARNING : still subject to testing - especially symmetries.

Did the warnings have much impact on the outcome?hHow to remove this warning?

My pseudopotential is ONCVPSP-PBE-PDv0.4.

My input file

ndtset 3

# Set 1 : Initial self-consistent run

kptopt1 1

tolvrs1 1.0d-18 #need excellent convergence of GS quantities for RF runs

optdriver1 0

# Set 2 : Calculate the ddk wf's - needed for piezoelectric tensor and

# Born effective charges in dataset 3

getwfk2 -1

iscf2 -3 #this option is needed for ddk

kptopt2 2 #use time-reversal symmetry only for k points

nqpt2 1 #one wave vector will be specified

qpt2 0 0 0 #need to specify gamma point

rfelfd2 2 #set for ddk wf's only

rfdir2 1 1 1 #full set of directions needed

tolwfr2 1.0d-20 #only wf convergence can be monitored here

optdriver2 1

# Set 3 : response-function calculations for all needed perturbations

getddk3 -1

getwfk3 -2

kptopt3 2 #use time-reversal symmetry only for k points

nqpt3 1

qpt3 0 0 0

rfphon3 1 #do atomic displacement perturbation

rfatpol3 1 5 #do for all atoms

rfstrs3 3 #do strain perturbation

rfdir3 1 1 1 #the full set of directions is needed

tolvrs3 1.0d-10 #need reasonable convergence of 1st-order quantities

optdriver3 1

#Common input data

# acell COPY RELAXED RESULT FROM PREVIOUS CALCULATION

# Here is a default value, for automatic testing : suppress it and fill the previous line

acell 7.8195376106E+00 7.6804731029E+00 7.8158140311E+00

rprim 9.9999084672E-01 -2.6428541435E-19 -4.2786066027E-03

6.1232339957E-17 1.0000000000E+00 0.0000000000E+00

-1.3440657856E-02 6.1763458541E-17 9.9990967028E-01

#Definition of the atom types and atoms

npsp 4

znucl 82 8 40 22

ntypat 3

ntypalch 1

mixalch 0.52 0.48

natom 5

typat 1 2 2 2 3

#Starting approximation for atomic positions in REDUCED coordinates

#based on ideal tetrahedral bond angles

# xred COPY RELAXED RESULT FROM PREVIOUS CALCULATION

# Here is a set of default values, for automatic testing : suppress it and fill the previous line

xred 5.7985553951E-02 5.4187599351E-19 -6.4812601329E-02

4.7095252908E-01 4.8629243633E-19 5.2032924011E-01

-1.2118344632E-02 5.0000000000E-01 5.2214654756E-01

4.6928549538E-01 5.0000000000E-01 3.7931124251E-03

5.1389476621E-01 5.0000000000E-01 4.7854370124E-01

#Definition of the plane wave basis set

ecut 30 # Maximum kinetic energy cutoff (Hartree)

ecutsm 0.5 # Smoothing energy needed for lattice paramete

# optimization. This will be retained for

# consistency throughout.

pawecutdg 36

#Definition of the k-point grid

kptopt 1 # Use symmetry and treat only inequivalent points

ngkpt 8 8 8 # 4x4x4 Monkhorst-Pack grid

nshiftk 1 # Use one copy of grid only (default)

shiftk 0.0 0.0 0.5 # This choice of origin for the k point grid

# preserves the hexagonal symmetry of the grid,

# which would be broken by the default choice.

#Definition of the self-consistency procedure

diemac 4.0 # Model dielectric preconditioner

nstep 60 # Maxiumum number of SCF iterations

# enforce calculation of forces at each SCF step

optforces 1

Thanks for your reading.Looking forward for your help.

Best wishes.