! E01: the simplest possible SCF, on diamond-structure silicon.
! Two atoms, the three mandatory namelists, the three mandatory cards.
! Every later example builds on this file.

&CONTROL
  calculation  = 'scf'        ! one self-consistent run, no ionic motion
  prefix       = 'si'         ! basename under outdir; follow-up runs must reuse it
  outdir       = './tmp/'     ! scratch: charge density + wavefunctions land here
  pseudo_dir   = './pseudo/'  ! where the .UPF pseudopotential files live
  verbosity    = 'high'       ! print symmetry ops, k-point list (always 'high' while learning)
  tprnfor      = .true.       ! print forces (zero here by symmetry, but learn to check)
  tstress      = .true.       ! print the stress tensor (it reports on the lattice constant)
/
&SYSTEM
  ibrav        = 2            ! fcc Bravais lattice; primitive vectors follow QE's convention
  celldm(1)    = 10.26        ! cubic lattice constant a, in BOHR (= 5.43 Angstrom, experimental)
  nat          = 2            ! atoms in the cell
  ntyp         = 1            ! atomic species
  ecutwfc      = 30           ! wavefunction cutoff in Ry (converge it yourself in E3)
  ecutrho      = 240          ! density cutoff: 8 x ecutwfc, the PAW/US rule (4x default is for NC)
  occupations  = 'fixed'      ! integer occupations: a semiconductor with a gap
/
&ELECTRONS
  conv_thr     = 1.0d-8       ! SCF threshold in Ry (1e-6 default is too loose once forces matter)
  mixing_beta  = 0.7          ! aggressive mixing; fine for a simple insulator
/

! label | mass in amu (physical only in MD and phonons) | UPF file
ATOMIC_SPECIES
  Si  28.0855  Si.pbe-n-kjpaw_psl.1.0.0.UPF

! coordinates in units of celldm(1) ('alat').
! diamond = fcc lattice + two-atom basis at (0,0,0) and (1/4,1/4,1/4)
ATOMIC_POSITIONS (alat)
  Si  0.00  0.00  0.00
  Si  0.25  0.25  0.25

! Monkhorst-Pack grid nk1 nk2 nk3, then three 0/1 shifts (unshifted here).
! symmetry reduces 8x8x8 = 512 points to 29 irreducible ones.
K_POINTS (automatic)
  8 8 8  0 0 0