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PWmat can be used to study the following problems: (1) crystal band structure; (2) electronic density of state; (3) cohesive energy of crystal compounds; (4) alloy phase diagram; (5) phonon spectrum; (6) defect formation energy and defect state; (7) surface reconstruction and surface energy; (8) molecule-surface attachment and structure; (9) band alignment; (10) superlattice; (11) quantum confinement effect; (12) liquid free energy; (13) molecule or ion diffusion in liquid; (14) cluster structural search; (15) crystal or other structural search; (16) thermal conductivity; (17) catalytical pathway and intermediate states; (18) chemical reaction path and reaction energy; (19) organic molecule structures. This is just a partial list, many other properties can be added on. Some of these calculations are just a straight forward application of PWmat, some others need some analysis based on PWmat calculations. All these calculations will be based on the following basic PWmat calculations (JOB=): SCF, NONSCF, DOS, RELAX, MD, NEB. Here, we show some simple examples calculated using PWmat. It highlights what can be done using PWmat package

A 63 atom ZnO (bulk ZnO with one O vacancy) and the defect level isosurface. The atomic relaxation of this system takes 13 minutes with one GPU.

The atomic relaxation steps of the above 63 atom ZnO problem.

A dye molecule on top of a ZnO (10-10) surface. The whole system contains 148 atoms.

The total and partial density of state of the above ZnO O vacancy system. The Fermi energy is around -2.5 eV.

The total DFT energy (y axis, eV) of the dye-molecule/ZnO system as a function of the relxation steps.

The average atomic force (y axis, eV/A) as a function of the relaxation steps

(x axis) for the above dye-molecule/ZnO system. 8300 seconds are used to finish the 100 relaxation steps on a 2 GPU machine.

The total energy Etot and the potential energy (DFT energy) Ep (both in eV) as functions of the MD simulation steps (1 fs per step) under a Verlet algorithm. The total energy is conserved. It takes about 8317 seconds for finish 100 MD steps on a 2 GPU machine for the above 512 atom GaAs problem (83 second/MD step).

A 512 atom GaAs bulk system simulated with ab initio molecular dynamics at room temperature.

The total energy convergence curve during atomic relaxation steps (including the trial steps). The high spikes are due to initial steps in restarting the calculations. The system is a 229 atom Cu surface with Cu islands passivated by CO molecules. It takes 45 GPU to relax the whole system in 5 hours until about 1 meV total energy convergence. The vertical axis is the total energy (shifted) in eV, the horizontal axis is the relaxation steps.

The 229 atom Cu surface model with an Cu island passivated by CO molecules.

This is a convergence plot for a NEB relaxation for the maximum force as a function of the iteration steps (index of the number of line-minimizations, x-axise). The y-axis is the maximum force in eV/A. This is for a 63 atom Si system (one Si vacancy in a original 64 atom Si supercell). It is a NEB run for a transition of one nearest Si jump to the vacancy site. It uses 7 image configurations. The whole NEB calculation takes about 22 minutes on 1 GPU.

This is the energy plot along the image path of a NEB calculation (for the Si atom jumping to a neighboring vacancy in a 63 atom cell). The y-axis is the total energy (eV), the x-axis is the index of the images (the Nimage=7 in this calculation). From this plot, one can

find the transition barrier height.

This is the partial charge density of 1000GaAs with a Ga hole. The system has 3995 electrons, spending 2 hours with 16 relax steps to make the force less than 0.01eV/A on MSTATION.

This is a nanotube system with 532 carbon atoms, 2128 electrons. The FFT grids is 80*80*210. The relaxation of the system spends 2385s, 41steps to make the force less than 0.01eV/A.

This two pictures show 255GaAs (with one Ga vacancy) system's relaxation with HSE06 calculation. PWmat can relax the max force of all atoms to 0.01eV/A in 56 steps using 7885 seconds (about 2 hours!)