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exercises:2016_uzh_cmest:faq [2016/11/30 12:24] – created tmuellerexercises:2016_uzh_cmest:faq [2020/08/21 10:15] (current) – external edit 127.0.0.1
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 In some cases (for example for tin) there is only a short-range basis set available, called ''DZVP-MOLOPT-SR-GTH''. In some cases (for example for tin) there is only a short-range basis set available, called ''DZVP-MOLOPT-SR-GTH''.
  
-You can find all available MOLOPT basis sets in ''BASIS_MOLOPT'' which is located in the folder ''$CP2K_DATA_DIR'' (after loading the CP2K module).+You can find all available MOLOPT basis sets in ''BASIS_MOLOPT''which is located in the folder ''$CP2K_DATA_DIR'' (after loading the CP2K module). 
 + 
 +===== How do I run CP2K in parallel? ===== 
 + 
 +The command ''cp2k.sopt'' is the single-process variant of CP2K. 
 + 
 +To run CP2K in parallel, you have to use a different executable named ''cp2k.popt'' and prefix that with ''mpirun -n 8'' to run it on 8 CPUs in parallel. So, a complete command line to run CP2K on 8 CPUs would then be: 
 + 
 +<code> 
 +$ mpirun -n 8 cp2k.popt -i yourinput.inp -o youroutput.out 
 +</code> 
 + 
 + 
 +===== How do I obtain a charge density difference? ===== 
 + 
 +In [[exercises:2016_uzh_cmest:basic_electronic_structure|Exercise 2]] a series of ''*.cube'' files was already produced for MOs. 
 +To obtain the electronic charge density in a ''*.cube'', file the following snippet of input file can be used (see also the [[https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/E_DENSITY_CUBE.html|reference manual]]): 
 +<code> 
 +&FORCE_EVAL 
 +  &DFT 
 +    &PRINT 
 +      &E_DENSITY_CUBE 
 +      &END E_DENSITY_CUBE 
 +      ... 
 +    &END PRINT 
 +    ... ... 
 +  &END DFT 
 +&END FORCE_EVAL 
 +</code> 
 + 
 +The [[tools:cubecruncher|cubecruncher]] tool can be used to obtain charge density differences. A precompiled executable is available on the server ''tcopt3'', its path being ''/users/scaravat/bin/cubecruncher.x''
 + 
 +The basic usage to obtain a charge density difference is: 
 +<code> 
 +$ /users/scaravat/bin/cubecruncher.x -i input.cube -o output.cube -subtract subsystem.cube 
 +</code> 
 + 
 +===== How do I build a slab model for a surface? ===== 
 + 
 +E.g. by using [[http://jp-minerals.org/vesta/en/|VESTA]]. 
 +A tutorial is available [[http://hjklol.mit.edu/content/building-slab-geometries-catalysis-vesta|here]]. 
 + 
 +Vesta comes preinstalled on ''tcopt3'', provided that you load the proper module. 
 +<code> 
 +$ module load vesta 
 +</code> 
 + 
 +===== How do I obtain the stress tensor? ===== 
 + 
 +You have to add the following snippet to the input file: 
 +<code> 
 +&FORCE_EVAL 
 +  ... 
 +  STRESS_TENSOR ANALYTICAL 
 +  &PRINT 
 +    &STRESS_TENSOR 
 +    &END STRESS_TENSOR 
 +  &END PRINT 
 +  ... 
 +&END FORCE_EVAL 
 +</code> 
 + 
 +<note tip>Your calculation should be set up in such a way that forces are being calculated: 
 +e.g. ''RUN_TYPE'' set to ''GEO_OPT'' or ''ENERGY_FORCE''; instead ''RUN_TYPE ENERGY'' won't work!</note> 
 + 
 + 
 +===== My calculation does not converge ===== 
 + 
 +==== ... and I use MULTIPLE_UNIT_CELL ==== 
 + 
 +  * first make sure that you actually need ''MULTIPLE_UNIT_CELL''. In case you want to do band structure calculation, you most definitely do **not** want it 
 +  * if you are sure that you need it, make sure that it is specified two times: once in the [[https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/SUBSYS/CELL.html#MULTIPLE_UNIT_CELL|''CELL'' section]] and a second time in the [[https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/SUBSYS/TOPOLOGY.html#desc_MULTIPLE_UNIT_CELL|''TOPOLOGY'' section]], otherwise your calculation may or may not converge 
exercises/2016_uzh_cmest/faq.1480508666.txt.gz · Last modified: 2020/08/21 10:15 (external edit)