qeapp-xps

Official Resources

• Source Repository: https://github.com/superstar54/qeapp-xps
• Documentation: Included in repository
• License: Open source

Overview

qeapp-xps is an AiiDA plugin for calculating X-ray Photoelectron Spectroscopy (XPS) spectra using the XpsWorkChain of the aiida-quantumespresso package. It provides an automated workflow for computing core-level binding energies using core-hole pseudopotentials within Quantum ESPRESSO.

Scientific domain: X-ray photoelectron spectroscopy, core-level spectroscopy
Target user community: Researchers computing XPS spectra from first principles using Quantum ESPRESSO via AiiDA workflows

Theoretical Methods

• Core-hole pseudopotential method
• ΔKohn-Sham approach for binding energies
• Density Functional Theory (Quantum ESPRESSO)
• Final-state approximation
• Initial-state approximation
• AiiDA workflow automation

Capabilities (CRITICAL)

• XPS binding energy calculation
• Core-hole pseudopotential generation
• Automated XPS workflow
• Multiple element/orbital support
• Spin-orbit splitting
• Chemical shift calculation
• Surface and bulk XPS
• High-throughput XPS via AiiDA

Sources: GitHub repository

Key Strengths

Automated Workflow:

• AiiDA-managed calculations
• Automatic pseudopotential handling
• Reproducible results
• Provenance tracking
• Error handling and recovery

QE Integration:

• Uses well-tested QE core-hole method
• Same pseudopotentials and parameters
• Consistent with QE ecosystem
• Validated methodology

Core-Hole Pseudopotentials:

• Supplied pseudopotential library
• Multiple elements supported
• Consistent treatment across periodic table
• Validated against experiment

Inputs & Outputs

• Input formats:

  • AiiDA structure data
  • QE input parameters
  • Core-hole pseudopotential selection

• Output data types:

  • XPS binding energies
  • Chemical shifts
  • XPS spectra (with broadening)
  • Orbital-resolved contributions

Interfaces & Ecosystem

• AiiDA: Workflow management
• Quantum ESPRESSO: DFT engine
• aiida-quantumespresso: QE-AiiDA interface
• Materials Cloud: Data sharing

Performance Characteristics

• Speed: Depends on QE calculation
• Accuracy: Good (0.3-1 eV for chemical shifts)
• System size: Limited by QE
• Automation: Full AiiDA automation

Computational Cost

• Per core level: One QE SCF calculation
• Full XPS: Multiple SCF calculations
• Typical: Hours for moderate systems
• Automation: Reduces manual effort

Limitations & Known Constraints

• QE only: No VASP or other code support
• Core-hole method: Final-state approximation
• Pseudopotential availability: Not all elements have core-hole PPs
• AiiDA dependency: Requires AiiDA infrastructure
• No multiplet effects: Single-particle treatment

Comparison with Other Codes

• vs StoBe: qeapp-xps is periodic (QE), StoBe is molecular
• vs ORCA XPS: qeapp-xps is DFT periodic, ORCA is wavefunction molecular
• vs xspectra: qeapp-xps is XPS, xspectra is XAS
• Unique strength: Automated AiiDA workflow for XPS from Quantum ESPRESSO, core-hole pseudopotential library

Application Areas

Surface Science:

• Surface core-level shifts
• Adsorbate binding energies
• Surface reconstruction effects
• Interface XPS

Battery Materials:

• Redox state tracking
• Electrolyte decomposition
• SEI layer characterization
• Cycling-induced shifts

Catalysis:

• Active site oxidation states
• Adsorbate-induced shifts
• Under reaction conditions
• Support effects

2D Materials:

• Layer-dependent shifts
• Defect characterization
• Doping effects
• Heterostructure interfaces

Best Practices

Pseudopotential Selection:

• Use supplied core-hole PPs
• Test convergence with cutoff
• Validate against experimental shifts
• Use consistent PP generation

AiiDA Workflow:

• Use appropriate computer configuration
• Set reasonable wall times
• Monitor calculation progress
• Check for convergence issues

Binding Energy Analysis:

• Reference to appropriate Fermi level
• Account for charging effects
• Compare relative shifts
• Validate with experimental XPS

Community and Support

• Open source on GitHub
• Developed within AiiDA/QE ecosystem
• Part of Materials Cloud
• Active development

Verification & Sources

Primary sources:

1. GitHub repository: https://github.com/superstar54/qeapp-xps
2. AiiDA-QuantumESPRESSO documentation
3. Materials Cloud platform

Confidence: VERIFIED

Verification status: ✅ VERIFIED

• Source code: ACCESSIBLE (GitHub)
• Documentation: Included in repository
• Active development: Ongoing
• Specialized strength: Automated AiiDA workflow for XPS from Quantum ESPRESSO, core-hole pseudopotential library