[Pw_forum] magic cell size in FPMD

[Davide Ceresoli]

I'm running a simple calculation (1 atom in a cubic cell),
in serial, on a PC, and vary the cell size (celldm(1)).

celldm(1) = 18.897261     (10 angstrom) everything is fine!
celldm(1) = 18.0          crashes when writing restart to disk
celldm(1) = 18.8          crashes when writing restart to disk
celldm(1) = 19.0          crashes when writing restart to disk
celldm(1) = 22.676714     (20 angstrom) crashes when writing restart to disk

It's FPMD from CVS (end of september 2005), compiled with intel 8.1.
Debugger tells me it stops in Modules/mp_wave.f90:116
114      DO I = 1, ngwl
115        ! WRITE( stdout,*) 'MW ', ig_l2g(i), i
116        PWT( ig_l2g(i) ) = pw(i)
117      END DO


Luckily, up to now, I've always been using 10 angstroms!

Here is a sample input file:
  &control
     	title = 'hydrogen atom'
	prefix = 'h_sic'
     	calculation = 'cp'
     	restart_mode = 'from_scratch'
     	ndr = 50
     	ndw = 50
     	nstep = 100
     	iprint = 10
     	isave = 2
     	tstress = .true.
     	tprnfor = .true.
     	dt = 2.0
     	etot_conv_thr = 1.d-9
	outdir = './output/'
	pseudo_dir = './'
  /
  &system
         ibrav = 1
         celldm(1) = 18.897261
         nat = 1
         ntyp = 1
         ecutwfc = 40.0
         nbnd = 1
         nspin = 2
	nelup = 1
         neldw = 0
	nelec = 1
	ecutwfc = 80.0
	xc_type = 'PW'
         sic = 'sic_mac'
         force_pairing = .true.
  /
  &electrons
    	emass = 400
     	emass_cutoff = 2.5
     	orthogonalization = 'ortho'
     	ortho_eps = 5.d-8
     	ortho_max = 15
     	electron_dynamics = 'sd'
     	!electron_dynamics = 'damp'
	!electron_damping = 0.2
     	electron_velocities = 'zero'
     	electron_temperature = 'not_controlled'
	startingwfc = 'atomic'
  /
  &ions
     	ion_dynamics = 'none'
     	ion_radius(1) = 0.8d0
	ion_velocities = 'zero'
     	ion_temperature = 'not_controlled'
	sic_rloc = 1.0
  /
  &cell
     	cell_dynamics = 'none'
     	cell_velocities = 'zero'
     	press = 0.0
     	wmass = 70000.0
  /
ATOMIC_SPECIES
H    1.0    H.blyp-vbc.UPF

K_POINTS gamma

ATOMIC_POSITIONS angstrom
H     0.0000    0.0000    0.0000  0 0 0 1

EOF