input_file

# CP2K Input File

Documentation of cp2k can be found on the website http://manual.cp2k.org and can also be generated by the cp2k executable itself using the flag –html or –xml (followed by xml2htm if you want an html documentation). The documentation generated by the executable is always consistent with its version, whereas the one on the website refers to the latest version.

## Input Syntax

• the input is subdivided in sections that start with “&” and end with “&END”
• each section can contain other sections and keywords followed by values
• both the section names and the keyword names are case insensitive
• the special characters “#” and “!” denote the beginning of a comment that goes until the end of the line
• If the value of the keyword is experssed in units, perceding the value by the units in square bracket changes them. In the square brackets the units should have no space. For example “[m]” switches to meters.
• A long line of input can be split using the “\” character at the end of the line
• keywords with a logical value (flags), often have a value that is false when the keyword is missing; the value true when one writes just the keyword (lone_keyword_value), or they can be given an explicit value after the keyword as normal (for example KEYWORD FALSE).
• Sections can have a default parameter that comes right after the section value. For example the OT section has a logical default parameter that controls the activation of the OT method. So,
&OT
...
&END OT

activates the OT method and

&OT FALSE
...
&END OT

(or the absence of the OT section) deactivates it.

## Input Structure

The basic idea of the input is to define the options for the method that you want to use to calculate the forces/energy in the FORCE_EVAL section. If you use the ab-initio DFT part then the DFT and QS subsections will probabily be of interest for you. The method to use is choosen with FORCE_EVAL%METHOD keyword, i.e. the keyword METHOD in the FORCE_EVAL section. So you can easily switch from one method to the another if you gave meaningful parameters to both.

Then parameters for the kind of calculation (run type) to do using that method (energy,force,molecular dynamics,langevin,…) are defined in the MOTION section

Finally in the GLOBAL section you can choose the run type to perform with the keyword RUN_TYPE, the name of the project (PROJECT), used to generate most of the output files, the PRINT_LEVEL keyword that controls the general level of output, and other general flags. The GLOBAL%PRINT%PHYSCON keyword enables a printout of the physical constants used by cp2k.