Dear vahid I know in siesta, system when relaxed drop in local state not a global state. Moreover, total energy should not change a lot.
best regards homa ________________________________ From: Vahid Askarpour <[email protected]> To: [email protected] Sent: Tuesday, November 6, 2012 10:08 PM Subject: [SIESTA-L] Energy convergence in variable-cell relaxation Dear Siesta Users, Somehow my first email yesterday never made it to the forum so I am resubmitting my question in case no one has received it I am using the following Zmatrix.data: LatticeConstant 1.0 Ang %block LatticeVectors 6.280434196 -0.005586432 0.001779433 -0.010035350 10.640250385 -0.140887455 0.002995775 -0.139896936 10.441268506 %endblock LatticeVectors ZM.UnitsLength Ang ZM.UnitsAngle rad %block Zmatrix molecule_cartesian 1 0 0 0 3.26412488 0.18434288 8.34284764 1 1 1 2 1 0 0 1.65828859 2.90193293 -1.90908700 1 1 1 molecule_cartesian 1 0 0 0 3.00128916 5.56719236 3.03112031 1 1 1 2 1 0 0 1.66353716 2.91485149 -1.24973899 1 1 1 molecule_cartesian 1 0 0 0 3.60753463 0.02717187 2.80841061 1 1 1 2 1 0 0 1.66906300 2.58058615 -2.97842135 1 1 1 molecule_cartesian 1 0 0 0 2.65255564 5.27969113 7.97252916 1 1 1 2 1 0 0 1.66678629 2.61640917 -0.16745125 1 1 1 molecule_cartesian 1 0 0 0 1.14859333 9.24514323 3.66253191 1 1 1 2 1 0 0 1.67686751 1.59027708 -2.17167021 1 1 1 molecule_cartesian 1 0 0 0 5.06965174 1.28297685 3.79833399 1 1 1 2 1 0 0 1.67453554 1.66224662 0.98895492 1 1 1 molecule_cartesian 1 0 0 0 5.10773991 3.86224401 8.95287684 1 1 1 2 1 0 0 1.66720020 1.62595003 -1.01568338 1 1 1 molecule_cartesian 1 0 0 0 1.17918714 6.56017549 8.95228834 1 1 1 2 1 0 0 1.67350997 1.63380731 2.18415723 1 1 1 the following input.fdf: SystemName HI SystemLabel HI NumberOfSpecies 2 NumberOfAtoms 16 %block ChemicalSpeciesLabel 1 1 H 2 53 I %endblock ChemicalSpeciesLabel PAO.BasisSize DZ kgrid_cutoff 12.0 Ang MeshCutoff 120 Ry PAO.EnergyShift 0.002 Ry %include mydefaults.fdf # DFT, Grid, SCF XC.functional GGA XC.authors PBE MaxSCFIterations 1000 DM.MixingWeight 0.150 DM.Tolerance 1.d-5 DM.NumberPulay 5 # Number of SCF steps between pulay mixing # Relaxation, smearing, etc. ElectronicTemperature 300 K MD.TypeOfRun cg # Type of dynamics Optim.Broyden .true. MD.VariableCell .true. MD.ConstantVolume .false. MD.MaxForceTol 1d-5 eV/Ang MD.NumCGsteps 200 Use-Save-CG .true. Use-Save-XV .true. MD.Broyden.Initial.Inverse.Jacobian 0.20 MD.RemoveIntramolecularPressure .true. #MD.PreconditionVariableCell 10.0 Ang MD.TargetPressure 0.001 GPa # Treatment of the Z-matrix ZM.ForceTolLen 0.04 eV/Ang ZM.ForceTolAng 0.0001 eV/deg ZM.MaxDisplLen 0.1 Ang ZM.MaxDisplAng 20.0 deg AtomicCoordinatesFormat NotScaledCartesianAng %include Zmatrix.data and the following mydefaults.fdf: SpinPolarized .false. # Spin unpolarized calculation SolutionMethod diagon # OrderN or Diagon # Output options WriteCoorInitial .true. WriteCoorStep .true. WriteForces .false. WriteKpoints .false. WriteEigenvalues .false. WriteKbands .false. WriteBands .false. WriteMullikenPop 0 WriteCoorXmol .false. WriteMDCoorXmol .false. WriteMDhistory .false. # Options for saving/reading information DM.UseSaveDM .false. # Use DM Continuation files MD.UseSaveXV .false. # Use stored positions and velocities MD.UseSaveCG .false. # Use stored positions and velocities SaveRho .false. # Write valence pseudocharge at the mesh SaveDeltaRho .false. # Write RHOscf-RHOatm at the mesh SaveElectrostaticPotential .false. # Write the total elect. pot. at the mesh SaveTotalPotential .false. # Write the total pot. at the mesh WriteSiestaDim .false. # Write minimum dim to siesta.h and stop WriteDenchar .false. # Write information for DENCHAR After finishing the run, the enthalpy only changed between -4719.41 and -4719.49 but the volume changed between 696 and 716. In other words, the volume is changing but the energy remains unchanged. Shouldn't the energy reach a minimum as the structure is relaxed? Or perhaps I am missing something. Thank you for your suggestions. Vahid
