Angle Constraints Block
Constraining of angles in the constraints block does not seem to work properly.
If I am doing calculation with a cubic unit cell and trying to constrain all angles and varying the unit cell, then the relaxation goes on, but the lenght of the unit cell along z direction (third direction) does not change.
If I try to constrain only one angle (alpha), then the first unit cell vector gets fixed.
Below is the input fdf file. I am also attaching the corresponding output file.
SystemName siesta
SystemLabel siesta
NumberOfSpecies 1
NumberOfAtoms 4
%block ChemicalSpecieslabel
1 79 Au.gga.1
%endblock ChemicalSpecieslabel
%block PAO.BasisSizes
Au.gga.1 DZP
%endblock PAO.BasisSizes
LatticeConstant 1.0 Ang
%block LatticeVectors
4.080000000000000 0.000000000000000 0.000000000000000
0.000000000000000 4.080000000000000 0.000000000000000
0.000000000000000 0.000000000000000 4.080000000000000
%endblock LatticeVectors
AtomicCoordinatesFormat Ang
%block AtomicCoordinatesAndAtomicSpecies
0.000000000 0.000000000 0.000000000 1
0.000000000 2.040000000 2.040000000 1
2.040000000 0.000000000 2.040000000 1
2.040000000 2.040000000 0.000000000 1
%endblock AtomicCoordinatesAndAtomicSpecies
DM.NumberPulay 3
MaxSCFIterations 1000
DM.MixingWeight 0.1
DM.UseSaveDM False
%block Geometry.Constraints
cell-angle alpha
%endblock Geometry.Constraints
XC.functional GGA
XC.authors PBE
PAO.EnergyShift 0.10000000 eV
MeshCutoff 2721.1386 eV
SpinPolarized False
MD.TypeOfRun CG
MD.NumCGsteps 200
MD.MaxForceTol 0.04000000 eV/Ang
MD.VariableCell True
#KPoint grid
%block kgrid_Monkhorst_Pack
2 0 0 0.0
0 2 0 0.0
0 0 2 0.0
%endblock kgrid_Monkhorst_Pack