&control
    calculation = 'scf'
    tstress=.true.
 /
 &system
    ibrav=2, celldm(1) =10.20, 
    nat=2, ntyp=1,
    ecutwfc=12.0
 /
 &electrons
 /
ATOMIC_SPECIES
 Si  28.086  Si.pz-vbc.UPF
ATOMIC_POSITIONS {alat}
 Si 0.00 0.00 0.00
 Si 0.25 0.25 0.25
K_POINTS {Gamma}