1.1 Protocol specifications

Collect the specifications of the available protocols for each code.

Special protocol: verification-PBE-v1

The "verification-PBE-v1" protocol is a protocol where kpoints and smearing has been agreed among all codes. In particular:

• the kpoints set is generated from a distance of 0.06 1/Ang along each direction in reciprocal space (and it must include Gamma)
• the smearing is a Fermi-Dirac smearing with broadening of 0.0045 Ry.

The energy to compare is the free energy (F = E - TS) where T indicates the fictitious temperature due to the smearing.

All other parameters are "as converged as possible" and depend on the code algorithms, basis sets, ... Some details are outlined below; note that not all codes have optimised these parameters for efficiency (i.e., some parameters might be more expensive than necessary to make sure they are converged).

This protocol has used for the verification study in...(paper ref) and it is focused on precision rather than efficiency.

Siesta

draft

• verification-PBE-v1 Pseudopotential ONCVPSPv0.4 (norm-conserving) of Pseudo Dojo in psml format, fully relativistic, PBE and with standard accuracy. Optimized basis set on crystal elemnts. The threshold for convergence of the density matrix is 1.e-5.
• moderate Pseudopotential ONCVPSPv0.4 (norm-conserving) of Pseudo Dojo in psml format, scalar relativistic, PBE and with standard accuracy. See Pseudo Dojo website for more info (link). Basis set apply globally, with size DZ and energy-shift of 100 meV. Meshcutoff is 100 Ry, electronic temp 25 meV, and a kpoint mesh with distance 0.2 are implemented. Concerning the threshold for convergence, we implement 1.e-3 tolerance for the density matrix, 0.04 ev/ang for forces and 1 GPa for stress. This choice of parameters have been tested on crystal elements of the Delta test (link) and ...
• precise Pseudopotential ONCVPSPv0.4 (norm-conserving) of Pseudo Dojo in psml format, scalar relativistic, PBE and with stringent accuracy. See Pseudo Dojo website for more info (link). Basis set apply globally, with size DZP and energy-shift of 100 meV. Meshcutoff is 500 Ry, electronic temp 25 meV, and a kpoint mesh with distance 0.062 are implemented. Concerning the threshold for convergence, we implement 1.e-4 tolerance for the density matrix, 0.03 ev/ang for forces and 0.005 ev/ang^3 for stress. This choice op parameters have been tested on crystal elements of the Delta test (link) and ...