Input Generation
This tutorial explains how to prepare VASP and Quantum ESPRESSO calculation inputs with VQkit.
VQkit provides a unified pre-processing interface for:
creating new VASP calculations;
creating new Quantum ESPRESSO calculations;
converting CIF structures to VASP or QE input;
converting completed output structures back into new inputs;
preparing K-points and band paths;
assembling VASP POTCAR files from a local licensed library;
validating the generated inputs before job submission.
Important
VQkit generates starter inputs.
Always review the generated files before production calculations.
In particular, verify:
pseudopotentials;
plane-wave cutoffs;
k-point meshes;
spin settings;
smearing;
convergence thresholds;
structural constraints;
executable paths;
HPC scheduler settings.
1. Create a new calculation
Choose:
1
VQkit first asks:
Calculation Folder Name:
Example:
graphene_scf
VQkit creates a new directory with that name.
Then select the DFT code:
[1] VASP
[2] Quantum ESPRESSO
VASP input generation
Choose:
1
for VASP.
VQkit then asks how the INCAR should be prepared:
[1] Auto-created INCAR
Use VQkit standard settings
[2] Set up your own INCAR
Choose optimization type, cutoff and convergence criteria
Auto-created INCAR
Choose:
1
VQkit asks for the calculation type and creates a standard starter INCAR.
Supported VASP calculation intents include:
relax
static / SCF
DOS
band structure
SOC SCF
SOC DOS
SOC band structure
AIMD
NEB
custom
VQkit then creates:
INCAR
KPOINTS
job.sh
VQkit_SETUP.txt
For interactive setup, VQkit also guides the POSCAR/POTCAR stage.
Custom INCAR
Choose:
2
VQkit allows you to choose settings such as:
calculation type;
ENCUT;
electronic convergence;
ionic-force convergence;
k-point mesh.
The generated INCAR should still be reviewed for system-specific settings.
VASP KPOINTS
For ordinary SCF, relaxation, DOS, or similar calculations, VQkit creates a regular KPOINTS mesh from the selected mesh dimensions.
Example:
6 6 1
For a band-structure workflow, generate the high-symmetry path separately using the VQkit K-path workflow.
See:
Tutorials -> Band Structure
VASP POSCAR and POTCAR
Interactive VASP setup expects a valid structure.
VQkit can work from a POSCAR and assemble POTCAR from a locally configured VASP pseudopotential library.
Because VASP pseudopotentials are licensed, VQkit does not distribute POTCAR files.
The pseudopotential order must match the element order in POSCAR.
Create POTCAR from POSCAR
From Pre-processing choose:
[7] Create POTCAR from POSCAR
VQkit reads the species order in POSCAR and assembles the corresponding POTCAR from your local VASP pseudopotential library.
Always verify that the selected potentials are appropriate for your calculation.
VASP generated directory
A typical VASP starter directory may look like:
graphene_scf/
├── INCAR
├── KPOINTS
├── POSCAR
├── POTCAR
├── job.sh
└── VQkit_SETUP.txt
The setup note reminds you to verify the calculation parameters before submission.
Quantum ESPRESSO input generation
Choose:
2
for Quantum ESPRESSO.
VQkit provides a QE-native calculation menu.
Supported calculation types include:
[1] Geometry optimization (relax)
[2] SCF
[3] VC-relax
[4] NSCF
[5] DOS
[6] PDOS
[7] Band structure
[8] Optical properties
[9] Phonons
[10] Fermi surface
[11] Thermo_PW
[12] AIMD
[13] NEB
[14] Custom
VQkit writes starter inputs according to the selected workflow.
QE relax
For geometry optimization, VQkit creates:
relax.in
QE SCF
For an SCF calculation:
scf.in
QE VC-relax
For variable-cell relaxation:
vc-relax.in
QE NSCF
For a non-self-consistent calculation:
nscf.in
QE DOS
For DOS preparation, VQkit creates:
nscf.in
dos.in
The NSCF stage must be completed before running dos.x.
QE PDOS
For projected DOS:
nscf.in
pdos.in
The NSCF calculation must be completed before running projwfc.x.
QE band structure
For band structure:
bands.in
bands_pp.in
The high-symmetry K-path should be generated with the VQkit K-path workflow.
QE optical properties
For optical analysis:
optical_scf.in
epsilon.in
QE phonons
For phonon preparation:
scf.in
ph.in
QE Fermi surface
For Fermi-surface preparation:
nscf.in
fs.in
QE Thermo_PW
For Thermo_PW:
scf.in
thermo_control
QE AIMD
For AIMD:
aimd.in
QE NEB
For NEB:
neb.in
QE directory structure
VQkit also creates:
pseudo/
tmp/
job.sh
VQkit_SETUP.txt
A typical QE starter calculation may look like:
graphene_scf/
├── scf.in
├── pseudo/
├── tmp/
├── job.sh
└── VQkit_SETUP.txt
Editing QE starter inputs
Before running Quantum ESPRESSO, review the generated input.
VQkit explicitly reminds you to provide or verify:
ATOMIC_SPECIES;exact UPF filenames;
CELL_PARAMETERSor another valid lattice definition;ATOMIC_POSITIONS;converged
ecutwfc;converged
ecutrho;k-point or q-point settings.
Place the UPF files inside:
pseudo/
or update pseudo_dir to point to the correct pseudopotential library.
QE prerequisite stages
Some QE workflows require multiple calculation stages.
Examples:
DOS
SCF
↓
NSCF
↓
dos.x
PDOS
SCF
↓
NSCF
↓
projwfc.x
Band structure
SCF
↓
bands calculation
↓
bands.x / plotting stage
Phonons
SCF
↓
ph.x
VQkit generates the relevant starter files, but prerequisite stages must be completed in the correct order.
2. Convert CIF to input
From Pre-processing choose:
[2] Convert CIF to input file
VQkit asks which DFT code should receive the structure:
[1] VASP
[2] Quantum ESPRESSO
VASP CIF conversion
For VASP, VQkit converts the selected CIF structure to a VASP structure input.
The generated structure should be checked carefully for:
lattice vectors;
atom ordering;
fractional coordinates;
primitive versus conventional cell;
occupancy issues.
Quantum ESPRESSO CIF conversion
For QE, VQkit converts the CIF structure into a QE starter input containing the structural information.
After conversion, verify the pseudopotentials, cutoffs, and calculation parameters before running QE.
3. Convert output to input
From Pre-processing choose:
[3] Convert output file to input file
This workflow allows the final structure from a completed calculation to be reused.
Typical uses include:
relaxation -> SCF;
relaxation -> DOS;
relaxation -> band structure;
one optimization stage -> another stage;
export of a relaxed structure for another code.
VASP
VQkit can use completed VASP structural output such as the final relaxed structure and prepare it for a new input workflow.
Quantum ESPRESSO
VQkit can parse the final QE structure and convert it into a new QE input.
Always verify that the final structure corresponds to the calculation stage you intend to continue.
Structure editing
VQkit also provides structure-editing tools.
Freeze / fix atoms
Choose:
[4] Freeze / fix atoms
This workflow can add constraints to:
VASP structures;
Quantum ESPRESSO inputs.
Typical applications include:
fixing bottom slab layers;
constraining selected atoms;
preparing surface calculations.
Delete atoms
Choose:
[5] Delete atoms
This can be used for:
vacancy creation;
removing adsorbates;
deleting selected atoms from VASP or QE structures.
Always inspect the resulting atom count and species order.
Pre-flight input validation
Before submitting a generated calculation, run:
[6] Pre-flight calculation check
This is strongly recommended.
VASP pre-flight checks
VQkit can inspect items such as:
INCAR availability;
POSCAR structure consistency;
POTCAR species ordering;
KPOINTS validity;
ENCUT relative to POTCAR ENMAX;
presence of
job.sh.
A successful result may end with:
[READY]
Warnings produce:
[READY WITH WARNINGS]
Blocking problems produce:
[NOT READY]
QE pre-flight checks
For QE, VQkit checks items such as:
&CONTROL;&SYSTEM;&ELECTRONSwhen present;nat;ntyp;ATOMIC_SPECIES;ATOMIC_POSITIONS;lattice definition;
ecutwfc;ecutrho;K_POINTS;relaxation namelists;
smearing settings;
pseudo_dir;pseudopotential file existence;
outdir.
For ibrav = 0, VQkit checks that three CELL_PARAMETERS vectors are
present.
For a band calculation, it also checks whether the K_POINTS specification is appropriate for a band path.
Example: VASP SCF starter
Suppose you want to prepare a VASP SCF calculation.
Step 1 — Start VQkit
Run:
vqkit
Step 2 — Open Pre-processing
Enter:
1
Step 3 — Create a new calculation
Enter:
1
Step 4 — Name the folder
For example:
graphene_scf
Step 5 — Select VASP
Choose:
1
Step 6 — Choose INCAR mode
Choose either:
1 Auto-created INCAR
or:
2 Set up your own INCAR
Step 7 — Select SCF/static
Choose the static / SCF calculation type.
Step 8 — Provide the structure
Ensure the generated directory contains a valid:
POSCAR
Step 9 — Prepare POTCAR
Use your configured local pseudopotential library to create:
POTCAR
Step 10 — Run pre-flight check
From Pre-processing choose:
6
Fix all ERROR items before submission.
Example: QE DOS starter
Suppose you want to prepare a QE DOS calculation.
Step 1 — Create a new calculation
Open:
Pre-processing
Create a new calculation
Step 2 — Select Quantum ESPRESSO
Choose:
2
Step 3 — Choose DOS
Choose:
5
VQkit creates:
nscf.in
dos.in
pseudo/
tmp/
job.sh
VQkit_SETUP.txt
Step 4 — Edit nscf.in
Verify:
prefix;
outdir;
pseudo_dir;
ATOMIC_SPECIES;
UPF filenames;
CELL_PARAMETERS;
ATOMIC_POSITIONS;
cutoffs;
dense DOS k-point mesh.
Step 5 — Complete prerequisite SCF
The DOS workflow requires a valid SCF charge density before NSCF.
Step 6 — Run NSCF
Run the generated nscf.in after the SCF stage is available.
Step 7 — Run dos.x
After NSCF completes successfully, run:
dos.x < dos.in > dos.out
Step 8 — Analyze DOS with VQkit
Return to:
Post-processing
Electronic structure
DOS
Recommended workflow
A safe VQkit input-generation sequence is:
Prepare or import the structure.
Create the calculation.
Select the DFT code.
Select the calculation type.
Review all generated input parameters.
Add the required pseudopotentials.
Check K-points.
Check spin and smearing settings.
Run the VQkit pre-flight check.
Submit only after all blocking errors are resolved.
Scientific cautions
Generated defaults are not universal
A parameter suitable for one material may be inappropriate for another.
Always perform convergence testing where necessary.
Pseudopotentials
Use pseudopotentials appropriate for:
the exchange-correlation functional;
the chemical elements;
the desired valence configuration;
relativistic or SOC calculations where applicable.
K-point convergence
The generated K-point mesh is a starting point.
Converge the k-point density for the target property.
Plane-wave cutoff
Converge ENCUT in VASP or ecutwfc/ecutrho in QE.
Spin settings
Magnetic systems may require spin-polarized calculations and appropriate initial magnetic moments.
Smearing
Metallic and insulating systems generally require different occupation treatments.
HPC scripts
The generated job.sh is a starter script.
Adapt:
scheduler directives;
module loading;
executable paths;
MPI settings;
number of cores;
wall time
to your computing environment.