Quick reference (migration guide)¶

The quick reference tables compare how to set up calculations in AMS and standalone Quantum ESPRESSO. This can be useful if you are already familiar with Quantum ESPRESSO but want to use the AMS interface.

For details, see AMS driver’s tasks and properties or Quantum ESPRESSO Input, or the complete Examples.

Elements, coordinates, lattice, isotopes, charge, labels¶

One of the H atoms has a special label “H1”. Labels can be used to set atom-specific starting magnetizations or Hubbard U values (not shown here).

AMS

Standalone pw.x

# AMS Driver
System
  Atoms
    H 0. 0. 0. QE.Label=H1
    H 1. 0. 0. mass=2.01
  End
  Lattice
    6. 0. 0.
    0. 5. 0.
    0. 0. 4.
  End
  Charge 0
End

# pw.x
&SYSTEM
  ibrav = 0
  nat = 2
  ntyp = 2
  tot_charge = 0.0
/

CELL_PARAMETERS angstrom
  6. 0. 0.
  0. 5. 0.
  0. 0. 4.

ATOMIC_SPECIES
  H1 1.008 'H_ONCV_PBE-1.2.upf'
  H 2.01 'H_ONCV_PBE-1.2.upf'

ATOMIC_POSITIONS angstrom
  H1 0. 0. 0.
  H 1. 0. 0.

Pseudopotentials¶

AMS comes with a library of Quantum ESPRESSO pseudopotentials. The correct files will automatically be picked up when you specify the Family and Functional.

To see the available families or to specify your own pseudopotential files in AMS, see Pseudopotentials.

AMS	Standalone pw.x
Engine QuantumEspresso Pseudopotentials Family SG15 Functional PBE End EndEngine	# pw.x &CONTROL pseudo_dir='/some/path' / ATOMIC_SPECIES H1 1.008 'H_ONCV_PBE-1.2.upf' H 2.01 'H_ONCV_PBE-1.2.upf'

k-space sampling¶

Gamma-point (Γ-point) sampling:

AMS	Standalone pw.x
Engine QuantumEspresso K_Points gamma End EndEngine	# pw.x K_POINTS gamma

Monkhorst-Pack grid (4 x 4 x 4, shifted):

AMS	Standalone pw.x
Engine QuantumEspresso K_Points automatic 4 4 4 1 1 1 End EndEngine	# pw.x K_POINTS automatic 4 4 4 1 1 1

Energy cutoff¶

AMS	Standalone pw.x
Engine QuantumEspresso System ecutwfc 40 End EndEngine	# pw.x &SYSTEM ecutwfc = 40 /

Forces, stress tensor¶

AMS	Standalone pw.x
# AMS Driver Properties Gradients Yes StressTensor Yes End	# pw.x &CONTROL tprnfor = .true. tstress = .true. /

Singlepoint¶

AMS	Standalone pw.x
# AMS Driver Task SinglePoint	&CONTROL calculation = 'scf' /

Geometry optimization¶

Note: If you use AMS, it will not set calculation='relax' in the pw.x input. Instead it will use the internal AMS geometry optimizer and set calculation='scf'.

AMS	Standalone pw.x
# AMS Driver Task GeometryOptimization GeometryOptimization Method FIRE MaxIterations 100 End	# pw.x &CONTROL calculation = 'relax' nstep = 100 / &IONS ion_dynamics = 'fire' /

Constraints¶

Keep the position of the first atom fixed and the x-coordinate of the second atom fixed.

AMS	Standalone pw.x
# AMS Driver Constraints Atom 1 Coordinate 2 x End System Atoms H 0. 0. 0. H 1. 0. 0. End End	# pw.x ATOMIC_POSITIONS angstrom H 0. 0. 0. 0 0 0 H 1. 0. 0. 0 1 1

For more advanced constraints, see the AMS Driver documentation.

Execution¶

AMS

Standalone pw.x

#!/bin/sh
export SCM_DISABLE_MPI=1

rm -rf ams.results
$AMSBIN/ams <<EOF
Task SinglePoint

System
  Atoms
    H 0. 0. 0.
    H 1. 0. 0.
  End
  Lattice
    6. 0. 0.
    0. 5. 0.
    0. 0. 4.
  End
End

Engine QuantumEspresso
  Pseudopotentials
    Family SG15
    Functional PBE
  End
  System
    ecutwfc 40.0
    ecutrho 160.0
  End
  K_Points gamma
  End
EndEngine

EOF

echo Getting results...
# extract energy at end
RKF=quantumespresso.rkf
$AMSBIN/akf \
 ams.results/$RKF \
 -pv AMSResults%Energy

#!/bin/sh

# here show how to find
# the same pseudopotentials
# as on the left,
# but you can set PPDIR manually
PPDIR=`amspackages loc qe`
PPDIR=$PPDIR/upf_files/GGA/PBE
PPDIR=$PPDIR/SR/SG15-1.2/UPFs

$AMSBIN/startqe pw.x <<EOF
&CONTROL
  pseudo_dir='$PPDIR'
/

&SYSTEM
  ibrav = 0
  nat = 2
  ntyp = 1
  tot_charge = 0.0
  ecutwfc = 40
  ecutrho = 160
/

&ELECTRONS
/

ATOMIC_SPECIES
  H 1.008 'H_ONCV_PBE-1.2.upf'

ATOMIC_POSITIONS angstrom
  H 0. 0. 0.
  H 1. 0. 0.

CELL_PARAMETERS angstrom
  6. 0. 0.
  0. 5. 0.
  0. 0. 4.


K_POINTS gamma

EOF