About Kylin-PBC

Kylin-PBC is a periodic Density Functional Theory (DFT) program written in C++17, designed for high-accuracy electronic structure calculations of crystalline and periodic systems.

The program employs Gaussian-type orbital (GTO) basis sets with Goedecker-Teter-Hutter (GTH) pseudopotentials, and evaluates Coulomb and exchange integrals via advanced density fitting schemes: Multigrid Density Fitting (MGDF), Local Interpolative Separable Density Fitting (LSDF) and FFT-based Density Fitting (FTDF).

  • Exchange-correlation functionals: LDA, GGA, meta-GGA, Hybrid and RSH
  • Gamma-point (GRKS) and Monkhorst-Pack k-point sampling (KRKS) solvers
  • Adaptively Compressed Exchange (ACE) acceleration for hybrid functionals
  • Geometry optimization: BFGS quasi-Newton with trust radius control BFGS, RFO and GDIIS
  • Transition State Search: NEB and ci-NEB with FIRE Optimizer.
  • Occupation smearing schemes: Fermi-Dirac, Gaussian and Methfessel-Paxton
Kylin-PBC Logo

Technical Capabilities

Core algorithmic components powering Kylin-PBC

Exchange-Correlation Functionals

Full hierarchy of Kohn-Sham DFT approximations through Libxc integration. Supports local density approximation through range-separated hybrids, enabling systematic accuracy benchmarking across Jacob's ladder.

PBE SCAN B3LYP PBE0 HSE06 HF
Brillouin Zone Sampling

Monkhorst-Pack k-point meshes with automatic dispatch between Gamma-point (real-valued GRKS) and general k-point (complex-valued KRKS) solvers for optimal memory and computational efficiency.

GRKS KRKS MP-mesh
Integral Algorithms

Three complementary density fitting schemes: Multigrid Density Fitting (MGDF) for Coulomb and pseudopotential matrix evaluation, Local Interpolative Separable Density Fitting (LSDF) for exchange matrix construction, and FFT-based Density Fitting (FTDF) for efficient exact exchange computation.

MGDF LSDF FTDF
ACE & occ-RI Acceleration

Adaptively Compressed Exchange (ACE) operator with optional Cholesky decomposition and occupied-orbital Resolution of Identity (occ-RI) dramatically reduce the cost of hybrid functional SCF iterations while preserving numerical accuracy.

ACE occ-RI Cholesky Ewald-X
Geometry Optimization

Analytical nuclear gradient-driven structural relaxation with BFGS quasi-Newton Hessian updates, trust-radius step control, and GDIIS/GEDIIS geometry extrapolation for accelerated convergence.

BFGS RFO GDIIS GEDIIS
Transition State Search

Nudged Elastic Band (NEB) and Climbing Image NEB (CI-NEB) methods for locating minimum energy paths and transition states between reactant and product configurations on the potential energy surface.

NEB CI-NEB

Quick Start

Kylin-PBC requires two input files in the working directory: cell.txt (unit cell and atomic positions) and calc.txt (calculation parameters). Below is a minimal example for a silicon diamond single-point calculation.

cell.txt 
# Silicon diamond — lattice vectors (Angstrom)
3.8396000862    0.0000000000    0.0000000000
1.9198000431    3.3251912150    0.0000000000
1.9198000431    1.1083970717    3.1350203425
Cart
Si  0.000000000    0.000000000    0.000000000
Si  1.919800043    1.108397072    0.783755086
calc.txt 
SCF.xcfun           = PBE
SCF.basis           = dzvp-sr
SCF.psudo           = gth-pbe
SCF.kmesh           = 3 3 3
SCF.max_cycle       = 100
SCF.eps_engy        = 1e-8 [eV]
SCF.hks_mix_method  = BROY
SCF.smear_method    = fermi
SCF.smear_sigma     = 300 [K]