PAO.EnergyShift and PAO.SplitNorm

For some systems like CeO2 , even LDA+CA will over estimate the lattice lattice constant . For CeO2 , the experimental value of the lattice constant is 5.411A ,using LDA + CA ,the calculated value is 5.487 A ,while GGA+PBE is even much higher . However , I found that by increasing the values of PAO.EnergyShift and(or) PAO.SplitNorm , the value of the lattice constant will be decreased . I tested some other systems , they showed the same regularity , and I found in the main output that the value in block PAO.Basis will be changed correspondingly : when increasing the value of PAO.EnergyShift ,the first zeta will be decreased , and increasing the value of PAO.SplitNorm , other zeta will be decreased. I am confused now ,to adjust the values of PAO.EnergyShift and PAO.SplitNorm to get the proper lattice constant , but if there will be errors when calculating other properties ?

This is my in.fdf

SystemName CeO2

SystemLabel CeO2

NumberOfAtoms 12

NumberOfSpecies 2

%block ChemicalSpeciesLabel
 1 8 O
 2 58 Ce
%endblock ChemicalSpeciesLabel

##### BASIS DEFINITION #########################################################

PAO.BasisType split
PAO.BasisSize DZP

#%block PAO.BasisSizes
#%endblock PAO.BasisSizes

PAO.EnergyShift 0.02 Ry
 # Default value: 0.02 Ry

PAO.SplitNorm 0.15
 # Default value: 0.15

LatticeConstant 5.411 Ang

%block LatticeVectors
  1.000000000000000 0.000000000000000 0.000000000000000
  0.000000000000000 1.000000000000000 0.000000000000000
  0.000000000000000 0.000000000000000 1.000000000000000
%endblock LatticeVectors

AtomicCoordinatesFormat Fractional
%block AtomicCoordinatesAndAtomicSpecies
     0.250000000 0.250000000 0.250000000 1
     0.750000000 0.750000000 0.250000000 1
     0.750000000 0.250000000 0.750000000 1
     0.250000000 0.750000000 0.750000000 1
     0.250000000 0.250000000 0.750000000 1
     0.750000000 0.750000000 0.750000000 1
     0.750000000 0.250000000 0.250000000 1
     0.250000000 0.750000000 0.250000000 1
     0.000000000 0.000000000 0.000000000 2
     0.000000000 0.500000000 0.500000000 2
     0.500000000 0.500000000 0.000000000 2
     0.500000000 0.000000000 0.500000000 2
%endblock AtomicCoordinatesAndAtomicSpecies

XC.functional lda
 # Default value: LDA
XC.authors ca
 # Default value: PZ
#SpinPolarized .true.
 # Default value: .false.
MeshCutoff 225.0 Ry
 # Default value: 50 Ry
MaxSCFIterations 200
 # Default value: 50
DM.MixingWeight 0.1
 # Default value: 0.25
DM.NumberPulay 3
 # Default value: 0
DM.Tolerance 1.0d-4
 # Default value: 10**-4

SolutionMethod diagon
ElectronicTemperature 300 k
 # Default value: 300 K
MD.TypeOfRun CG
MD.VariableCell .true.
 # Default value: .false.
MD.NumCGsteps 200
 # Default value: 0
MD.MaxCGDispl 0.02 Ang
 # Default value: 0.2 Bohr
MD.MaxForceTol 0.02 eV/Ang
 # Default value: 0.04 eV/Ang

%block kgrid_Monkhorst_Pack
7 0 0 0.
0 7 0 0.
0 0 7 0.
%endblock kgrid_Monkhorst_Pack