Using the R.I.N.G.S. code it possible to study amorphous as well as crystalline structures.

Nevertheless the calculations for crystalline structures are slightly different and more CPU time consuming than the standard ones for amorphous structures.

Since calculations are simplified for amorphous structures we decided to use an option in order to activate or deactivate the computations for crystalline structures.

Note otherwise that crystalline groups as well as crystalline positions are not accepted by the R.I.N.G.S. code.

It is mandatory to provide a complete 3D model of the system to be studied.

**In the R.I.N.G.S. code the default option for computations is to study amorphous cells and not crystalline cells ! **

Thus in order to study crystalline structures with the R.I.N.G.S. code a very simple procedure as to be followed:

- Edit and modify the "parameters.F90" file located in the "rings-code/src" directory
- Build and install a version (serial or MPI) of the so-modified R.I.N.G.S. code
- Specify complete lattice parameters inlcuding lattice angles in the 'input' file.
- Run the modified R.I.N.G.S. code on the crystalline structure

The detailed procedure is describe thereafter.

- Edit and modify the "parameters.F90" file located in the "rings-code/src" directory:
- This file contains the declaration of almost all variables used for in the R.I.N.G.S. code.
- Locate and modify the following lines:

146**LOGICAL**:: GLASS**=**.true. ! 1/0 'cubic' (90/90/90) cell or not

**in**

146**LOGICAL**:: GLASS**=.false.**! 1/0 'cubic' (90/90/90) cell or not

- It is also possible to use fractional coordinates, in such case the coordinates can be given in term of the [lattice parameters] then the coordinate (0,0,0) is one corner of the simulation box,

or in term of the [lattice parameters]/2.0 then the coordinate (0,0,0) is the center of the simulation box.

When the coordinates are fractionals of the lattice parameters (corner 0,0,0) then the values of the coordinates are ranging between 0.0 and 1.0

When the coordinates are fractionals of the [lattice parameters]/2 (center 0,0,0) then the values of the coordinates are ranging between -1.0 and 1.0

The default option in the RINGS code is to use fractional coordinates of the [lattice parameters] then the point having (0,0,0) for coordinate is a corner of the simulation box,

nevertheless it is possible to modify this option by editing the file "parameters.F90":238

**INTEGER**:: FRACTYPE**=**0 ! Fractional coordinates:

! 0 : box corner has coordinate (0,0,0)

! 1 : box center has coordinate (0,0,0)

**in**238

**INTEGER**:: FRACTYPE**=**1 ! Fractional coordinates:

! 0 : box corner has coordinate (0,0,0)

! 1 : box center has coordinate (0,0,0) - Build and install a version (serial or MPI) of the so-modified R.I.N.G.S. code ex:
]$ ./configure --with-mpi FC=ifort MPIFC=mpif90 FCFLAGS="-O3 -mtune=core2"

]$ make

]$ make install - Check lattice parameters and in particular lattice angles in the 'input' file:
`... 0 # 6.75 6.75 6.75 # 90.0 90.0 90.0 # ...`

or

`... 1 # 6.75 0.00 0.00 # 0.00 6.75 0.00 # 0.00 0.00 6.75 # ...`

- Run the modified R.I.N.G.S. code on the crystalline structure
]$ cd MY_WORKING_DIRECTORY

]$**rings**my-input

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