Chapter 1 Introduction
ABACUS (Atomicorbtial Based Abinitio Computation at UStc) is an opensource computer code package aiming at largescale electronicstructure simulations from first principles, developed at the Key Laboratory of Quantum Information, Unviersity of Science and Technology of China (USTC). ABACUS uses normconserving pseudopotentials to describe the interactions between nuclear ions and valence electrons. As its name indicates, ABACUS primarily employs numerically tabulated atomcentered orbitals as its basis functions to expand electronic wave functions. These basis functions are generated using an optimization scheme developed by Chen, Guo, and He (CGH) [1] early on, and form a series of hierarchical basis sets, through
which the computational accuracy can be systematically improved by increasing the basis set size. Besides atomic basis sets, ABACUS also allows to use planewave basis set as an alternative option. This dual basisset feature allows for a convenient consistency and accuracy check within ABACUS.
Currently ABACUS provides the following features and functionalities.
• Groundstate total energy calculations using KohnSham (KS) density functional theory
(DFT) [2, 3] with localdensity or generalized gradient approximations (LDA/GGAs).
• Brillouin zone sampling using the MonkhorstPack special kpoints [4].
• Geometry relaxation with both Conjugated Gradient (CG) and BroydenFletcherGoldfarb Shanno (BFGS) [5] methods.
• Semiemperical van der Waals energy correction using the Grimme DFTD2 [6] scheme.
• NVT molecular dynamics simulation using the Nos´eHoover thermostat [7].
Other functionalities including hybrid density functionals and timedependent DFT are under active development, and will be available for the next release.
ABACUS can run both on desktop computers and high performance supercomputers, for the moment under the unit/linuxbased environment. It scales up to O(10^3) CPU cores.
For any use of ABACUS, please cite the following paper,
[1] M. Chen, GC Guo, and L. He, Systematically improvable optimized atomic sets for ab initio calculations, J. Phys.: Condens. Matter 22, 445501(2010).
[2] P. F. Li, X. H. Liu, M. H. Chen, P. Z. Lin, X. G. Ren, L. Lin, and L. He, Largescale ab initio simulations based on systematically improvable atomic
basis, Comput.Mater. Sci., in print; DOI:10.1016/j.commatsci.2015.07.004
