[CP2K:9588] KEEP_ANGLES not possible in CELL_OPT using BFGS

[Tobias Binninger]

Hi Matthias,

I am using CP2k version 4.1.
Here is an example input showing the problem:

&GLOBAL
  PROJECT SnO2
  RUN_TYPE CELL_OPT
  PRINT_LEVEL LOW
&END GLOBAL

&FORCE_EVAL
  METHOD QS
  STRESS_TENSOR ANALYTICAL

  &SUBSYS
    &CELL
      ABC 5.0 5.1 3.3
      MULTIPLE_UNIT_CELL 3 3 4
    &END CELL
    &TOPOLOGY
      COORD_FILE_FORMAT XYZ
      COORD_FILE_NAME ATOM_POSITIONS_INPUT
      MULTIPLE_UNIT_CELL 3 3 4
    &END TOPOLOGY
    &KIND Sn
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q4
    &END KIND
    &KIND O
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q6
    &END KIND
  &END SUBSYS

  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    SPIN_POLARIZED T
    MULTIPLICITY 1
    &QS
      EPS_DEFAULT 1.0E-8
      METHOD GAPW
    &END QS
    &MGRID
      NGRIDS 5
      CUTOFF 800
      REL_CUTOFF 60
    &END MGRID
    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-06
      MAX_SCF 1000
      &OT
        ALGORITHM IRAC
        ENERGY_GAP 0.001
        PRECONDITIONER FULL_ALL
      &END OT
    &END SCF
    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
    &END XC
  &END DFT

&END FORCE_EVAL

&MOTION

  &CELL_OPT
    TYPE GEO_OPT
    MAX_DR    1.0E-03
    MAX_FORCE 1.0E-03
    RMS_DR    1.0E-03    
    RMS_FORCE 1.0E-03
    MAX_ITER 200
    KEEP_ANGLES  T
    OPTIMIZER BFGS
  &END CELL_OPT

  &GEO_OPT
    TYPE MINIMIZATION
    MAX_DR    1.0E-03
    MAX_FORCE 1.0E-03
    RMS_DR    1.0E-03    
    RMS_FORCE 1.0E-03
    MAX_ITER 200
    OPTIMIZER BFGS
  &END GEO_OPT

  &CONSTRAINT
    &FIXED_ATOMS
      COMPONENTS_TO_FIX XYZ
      LIST 1
    &END FIXED_ATOMS
  &END CONSTRAINT

&END MOTION

This is the first part of the output, showing that the angles already 
change in the first step:

 *******************************************************************************
 ***                     STARTING   CELL   
OPTIMIZATION                      ***
 ***                                   
BFGS                                  ***
 *******************************************************************************

 CELL| Volume [angstrom^3]:                                             
3029.400
 CELL| Vector a [angstrom]:      15.000     0.000     0.000    |a| =      
15.000
 CELL| Vector b [angstrom]:       0.000    15.300     0.000    |b| =      
15.300
 CELL| Vector c [angstrom]:       0.000     0.000    13.200    |c| =      
13.200
 CELL| Angle (b,c), alpha [degree]:                                       
90.000
 CELL| Angle (a,c), beta  [degree]:                                       
90.000
 CELL| Angle (a,b), gamma [degree]:                                       
90.000
 CELL| Numerically 
orthorhombic:                                             YES

 --------  Informations at step =     0 ------------
  Optimization Method        =                 BFGS
  Total Energy               =     -2561.1655488258
  Internal Pressure [bar]    =    -94313.1351913527
  Used time                  =             4260.816
 ---------------------------------------------------

 --------------------------
 OPTIMIZATION STEP:      1
 --------------------------

  Step is scaled; Scaling factor =  0.58939

 CELL| Volume [angstrom^3]:                                             
2942.352
 CELL| Vector a [angstrom]:      14.928     0.000     0.000    |a| =      
14.928
 CELL| Vector b [angstrom]:       0.000    15.220     0.000    |b| =      
15.220
 CELL| Vector c [angstrom]:       0.002     0.002    12.950    |c| =      
12.950
 CELL| Angle (b,c), alpha [degree]:                                       
89.993
 CELL| Angle (a,c), beta  [degree]:                                       
89.993
 CELL| Angle (a,b), gamma [degree]:                                       
90.000
 CELL| Numerically 
orthorhombic:                                              NO

Best regards,
Tobias
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