Molecular Dynamics( MD - Optimization ) Parallel Execution in QUANTUM ESPRESSO

Dear Friends, 

        In this session, we are going to see the unitcell optimization using the "Verlet ion dynamics  Parrinello-Rahman algorithm of lagrangian". Before executing groundstate studies we have to optimize the structure first. In this session, I used the same Silicon structure by changing some parameters in the input file.  In the calculation, I have defined as "vc_relax" which stands for structure relaxation. nstep has the control of iteration. we must have to fix the parameter of convergent accuracy in the iteration. and we have chosen MD optimization so we also have to define the mixing_beta this will have the control of volume or XYZ variation. 

we force the silicon ions to move along MD trajectory by applying the pressure. so our unitcell also a variable parameter. These workflows can be controlled by the following input parameters.

&IONS

  ion_dynamics  = 'damp'

/

&CELL

  cell_dynamics = 'damp-pr'        #damp-pr denotes Parrinello-Rahman algorithm of lagrangian

  press_conv_thr = 0.05

/

🔺 Note: we can also trace the ions on various the temperature by following notations in the input file.

&ions

ion_temperature='nose'         

          tempw=4000      

          fnosep=3.0  

Now, we can proceed to the parallel calculation. Open your command prompt by using Windows key + R →type CMD press Enter. Then go to your mpi source code directory by the cd command. Then execute the mpiexec.exe run command. now it will show you the cores, threads usage command for your PC. I have 4 core processors so its showing mpiexec -n 4. Then go to your program directory by cd commands. 

Now we can execute the mpi parallel execution run command as mpiexec -n 4 pw.exe < Si.in > Si.out 

Wait for a while the program as to run completely. Then Open your  Si.out file using notepad, scroll down and find the " End final coordinates" this is your optimized atomic lattice parameter and optimized structure.

We have to copy this ed final coordinates and paste them in the input file. Now, this input file can be visualize the crystal structure using the Xcrysden package. Thank you for supporting my blog.....!!🥰