  CONQUEST is a DFT code which was designed from the beginning to enable
extremely large-scale calculations on massively parallel platforms,
implementing both exact and linear scaling solvers for the ground state. It
uses local basis sets (both pseudo-atomic orbitals, PAOs, and systematically
convergent B-splines) and sparse matrix storage and operations to ensure
locality in all aspects of the calculation. Using exact diagonalisation
approaches and a full PAO basis set, systems of up to 1,000 atoms can be
modelled with relatively modest resources (200-500 cores), while use of
multi-site support functions (MSSF) enable calculations of up to 10,000 atoms
with similar resources. With linear scaling, the code demonstrates essentially
perfect weak scaling (fixed atoms per process), and has been applied to over
1,000,000 atoms, scaling to nearly 200,000 cores; it has been run on both the K
computer and Fugaku, among other computers. CONQUEST calculates the total
energy, forces and stresses exactly, and allows structural optimisation of both
ions and simulation cell. Molecular dynamics calculations within the NVE, NVT
and NPT ensembles are possible with both exact diagonalisation and linear
scaling[6]. The code interfaces with LibXC to implement LDA and GGA
functionals, with metaGGA and hybrid functionals under development. Dispersion
interactions can be included using semi-empirical methods (DFT-D2/3, TS) and
vdW-DF. The polarisation can be calculated using Resta's approach.
