ABACUS (Atomic-orbital Based Ab-initio Computation at USTC) is an open-source software package designed for large-scale electronic structure simulations from first principles. It has been developed by Prof. Lixin He's group at the Key Laboratory of Quantum Information, CAS, at the University of Science and Technology of China since 2007. Currently, developers from the Institute of Physics, CAS; Peking University; AISI Beijing; and the Hefei Institute of Artificial Intelligence are jointly contributing to the development of ABACUS.

 ABACUS uses norm-conserving pseudopotentials to describe the interaction between nuclear ions and valence electrons. As its name indicates, ABACUS primarily employs numerically tabulated atom-centered orbitals as the basis functions to expand electronic wave functions. These basis functions are generated using an optimization scheme developed by Chen, Guo, and He(CGH) early on, and they form a series of hierarchical basis sets, through which the computational accuracy can be systematically improved. Besides atomic basis sets, ABACUS also offers the plane-wave basis set option. This dual basis-set feature allows for a convenient consistency accuracy check within ABACUS.

 ABACUS currently provides the following features and functionalities:

1.      Three types of supported basis sets: pw, LCAO, and LCAO-in-pw.

2.      Ground-state total energy calculations using Kohn-Sham (KS) density functional theory (DFT) with local-density, generalized gradient approximations (LDA/GGAs), Meta-GGA(requires LIBXC), and hybrid functionals (PBE0 and HSE06, only for LCAO).

3.      Geometry relaxations with Conjugated Gradient (CG), BFGS, and FIRE methods.

4.      Semi-empirical van der Waals energy correction using the Grimme DFT-D2/D3 scheme.

5.      NVT and NVE molecular dynamics simulation. AIMD, DP potential, LJ potential are supported.

6.      Stress calculations and cell relaxations.

7.      Electric polarization calculation using Berry Phase theory.

8.      Interface to the Wannier90 package.

9.      Real-time time dependent density functional theory (TDDFT).

10.    Print-out of the electrostatic potential.

11.    Mulliken charge analysis (only for LCAO).

12.    Projected density of states (PDOS) (only for LCAO).

13.    DFT+U calculation (only for LCAO).

14.    Solvation model method for solvation energy.

15.    Stochastic DFT (only for PW).

16.    DeePKS method (under development, only for LCAO).

17.    Electric field and dipole correction.

18.    Orbital-free DFT.

19.    (subsidiary tool)Plot_tools for plot PDOS and PBANDS.

20.    (subsidiary tool)Generator for second generation numerical orbital basis.

21.    Interface with DPGEN

22.    Interface with phonopy

23.    Implicit solvation model

24.    More functions please refer to our manual

ABACUS can run both on desktop computers and high performance supercomputers under the unix/linux-based environment. The code is massively parallelized, scaling up to O(10^3) CPU cores.