mirror of https://gitlab.com/QEF/q-e.git
87 lines
3.9 KiB
Plaintext
87 lines
3.9 KiB
Plaintext
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Example calculation of water periodic box using PBE0 xc
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----------------------------------------------------
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In this example, we demonstrate how EXX calculations with maximally localized Wannier functions (MLWFs)
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can be performed for a 32 water periodic simulation box.
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Files included
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- 01.input and 02.input are two input files to run electron minimization and NVT MD, respectively.
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- 01.out and 02.out are two corresponding output files.
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- H_HSCV_PBE-1.0.UPF and O_HSCV_PBE-1.0.UPF are two pseudopotentials used to generate the outputs.
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- example-job-script is an example job submission script.
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----------------------------------------------------
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===== electron minimization =====
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----------------------------------------------------
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Here, we have performed a PBE0 electron minimization from_scratch
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using damped electron dynamics, keeping ions and cell fixed.
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The input file is 01.input and the corresponding output file is 01.out.
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The exx related keywords are highlighted in the input.
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In the output the exx related information is printed as:
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----------------------------------------------------
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Exact Exchange Using Wannier Function Initialization
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----------------------------------------------------
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The exx calculation requires MLWFs which are not present when the calculation starts from_scratch.
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So in the beginning, the calculation starts with PBE (no exx) to generate MLWFs.
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When the MLWFs are generated and sufficiently converged the calculation automatically
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switches to PBE0 by turning on exx. See in the output the following message:
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Exact Exchange is turned on ...
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When exx is activated the quantities related to exx are printed, for example
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nj_max nj_min nj_avg : 12 9 10.23
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The nj_max and nj_min refer to the maximum and minimum number of orbital pairs distributed over
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different MPI tasks. nj_avg is the total number of orbital pairs / number of MPI tasks.
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The computed exx energy multiplied with the exx_fraction is also printed in the 5th column of the
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energy printing line in the output. In this case the value at the final step is -31.505128874085 Hartree.
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The energies are also printed in the .evp file.
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At the end of the output file the time required to compute the exx energy is printed as
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exact_exchan : 948.10s CPU 555.95s WALL ( 53 calls)
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For this calculation we have used
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- 256 MPI tasks which is two times the number of electronic states of the system.
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- 2 OpenMP threads per MPI task
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- 2 task groups
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- ndiag is set to 121 which is the largest perfect square number less or equal to the number of electronic states.
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An example job submission script is added which is specific to Edison machine in NERSC.
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Similar parallelization scheme can be used in other architectures.
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For more information on the parallelization of exx calculations see the description of
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README-Parallelization or the user_guide in CPV/Doc/user_guide.tex.
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----------------------------------------------------
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===== Molecular dynamics =====
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----------------------------------------------------
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Using the minimized wavefunction one can start MD in various (NVE or NVT or NPT) ensembles.
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An example NVT input file 02.input and the corresponding output file 02.out are provided.
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The exx related keywords are the same as used in the electron minimization.
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For this calculation we have used
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- 256 MPI tasks which is two times the number of electronic states of the system.
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- 2 OpenMP threads per MPI task
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- 2 task groups
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- ndiag is set to 121 which is the largest perfect square number less or equal to the number of electronic states.
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----------------------------------------------------
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===== Questions / Comments / Feedback =====
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----------------------------------------------------
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You may send your queries to
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Biswajit Santra <bishalya@gmail.com>
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Hsin-Yu Ko <kosinyj@gmai.com>
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Robert A. DiStasio <robdistasio@gmail.com>
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