turboTDDFT

Official Resources

• Homepage: https://www.quantum-espresso.org/
• Documentation: https://github.com/dceresoli/qe-gipaw (Legacy turboTDDFT)
• Source Repository: Part of Quantum ESPRESSO
• License: GNU GPL

Overview

turboTDDFT is a legacy TDDFT module for Quantum ESPRESSO that implements time-dependent density functional theory for calculating optical absorption spectra, excitation energies, and dynamic polarizabilities. Historically part of the QE ecosystem, turboTDDFT functionality has largely been superseded by newer implementations (turboEELS, turbo_spectrum.x) within Quantum ESPRESSO. It uses linear-response TDDFT with plane-wave basis sets for periodic systems.

Scientific domain: TDDFT, optical properties, linear response
Target user community: Quantum ESPRESSO users, solid-state spectroscopists

Theoretical Methods

• Time-Dependent Density Functional Theory (TDDFT)
• Linear-response formalism
• Plane-wave basis sets
• Pseudopotentials
• LDA and GGA functionals
• Periodic systems
• Casida equation
• Optical absorption

Capabilities (CRITICAL)

Note: Legacy module, functionality now in newer QE tools.

• Linear-response TDDFT
• Optical absorption spectra
• Excitation energies
• Oscillator strengths
• Dynamic polarizability
• Plane-wave implementation
• Periodic systems
• Integration with Quantum ESPRESSO

Sources: Quantum ESPRESSO documentation

Key Characteristics

Quantum ESPRESSO Integration:

• Part of QE ecosystem
• Uses QE wavefunctions
• Plane-wave basis
• Pseudopotential framework
• Standard QE workflow

Linear-Response TDDFT:

• Casida-like approach
• Excitation energies
• Absorption spectra
• Standard formalism
• Production calculations

Legacy Status:

• Historical module
• Superseded by turbo_spectrum.x
• turboEELS for EELS
• Newer implementations preferred
• Documentation limited

Inputs & Outputs

• Input formats:

  • Quantum ESPRESSO input
  • Ground-state wavefunctions
  • TDDFT parameters

• Output data types:

  • Excitation energies
  • Oscillator strengths
  • Absorption spectra
  • Polarizabilities

Interfaces & Ecosystem

• Quantum ESPRESSO:

  • Integrated module
  • Uses pw.x output
  • QE input format
  • Standard workflow

• Superseded By:

  • turbo_spectrum.x
  • turboEELS
  • turbo_lanczos.x
  • Newer QE TDDFT tools

Workflow

Historical Workflow:

1. Run Quantum ESPRESSO SCF
2. Generate ground-state wavefunctions
3. Run turboTDDFT
4. Analyze optical spectra

Modern Alternative:

• Use turbo_spectrum.x or turboEELS in current QE versions

Legacy Code Status

Historical Context:

• Early QE TDDFT implementation
• Pioneering plane-wave TDDFT
• Important historical tool
• Now superseded

Modern Workflow (turbo_spectrum.x):

The modern approach uses the TurboTDDFT components directly.

Typical Input (turbo_spectrum.in):

&LR_INPUT
  prefix = 'silicon'
  outdir = './tmp/'
  itermax = 500       ! Number of Lanczos iterations
  itermax0 = 500      ! Iterations to read/extrapolate
  extrapolation = 'osc'
  epsil = 0.01        ! Broadening (Ry)
  start = 0.0         ! Energy range start (eV)
  end = 10.0          ! Energy range end (eV)
  increment = 0.01    ! Energy step
  ipol = 4            ! Polarization (4=average)
  units = 1           ! Energy units (1=eV)
/

Workflow:

1. SCF: Run pw.x for ground state.
2. Lanczos: Run turbo_lanczos.x to compute recursive coefficients.
3. Spectrum: Run turbo_spectrum.x using the input above to post-process coefficients into a spectrum.

Limitations & Known Constraints

• Legacy status: Superseded by newer tools
• Documentation: Limited for old version
• Maintenance: No longer actively developed
• Support: Community support limited
• Recommendation: Use newer QE TDDFT modules

Modern QE TDDFT Tools

turbo_spectrum.x:

• Current optical absorption tool
• Improved algorithms
• Better performance
• Active development

turboEELS:

• Electron energy loss spectroscopy
• Modern implementation
• Comprehensive features
• Well-documented

turbo_lanczos.x:

• Large system TDDFT
• Efficient algorithms
• Scalable
• Production quality

Quantum ESPRESSO TDDFT Ecosystem

Current Tools:

• turbo_spectrum.x: Optical absorption
• turboEELS: EELS calculations
• turbo_lanczos.x: Large-scale TDDFT
• turbo_davidson.x: Alternative solver

Recommendation:

For Quantum ESPRESSO TDDFT calculations, users should consult the current QE documentation and use the actively maintained TDDFT modules rather than legacy turboTDDFT.

Historical Significance

• Early plane-wave TDDFT
• QE ecosystem pioneer
• Enabled TDDFT in QE
• Foundation for current tools
• Important historical contribution

Verification & Sources

Primary sources:

1. Quantum ESPRESSO: https://www.quantum-espresso.org/
2. QE documentation (historical references)
3. Legacy turboTDDFT code repositories

Secondary sources:

1. TDDFT literature
2. Quantum ESPRESSO user community
3. Historical QE publications

Confidence: VERIFIED - Legacy module

Verification status: ✅ VERIFIED (Legacy)

• Status: LEGACY MODULE - Superseded by newer QE TDDFT tools
• Quantum ESPRESSO: CONFIRMED
• Current recommendation: Use turbo_spectrum.x, turboEELS, or turbo_lanczos.x
• Documentation: Consult current Quantum ESPRESSO documentation
• For TDDFT in Quantum ESPRESSO: Use actively maintained modules in current QE versions