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general_hints_-_frequently_asked_questions [2025/05/30 12:23] – [limit of 32 active orbitals] dollgeneral_hints_-_frequently_asked_questions [2025/07/15 11:08] (current) – [In a nutshell: how to start] doll
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   * W.J. Hehre, L. Radom, P.v.R. Schleyer, and J.A. Pople: Ab initio molecular orbital theory (Wiley, New York, 1986)   * W.J. Hehre, L. Radom, P.v.R. Schleyer, and J.A. Pople: Ab initio molecular orbital theory (Wiley, New York, 1986)
   * W. Kutzelnigg: Einführung in die Theoretische Chemie (Wiley-VCH, Weinheim, 2001)   * W. Kutzelnigg: Einführung in die Theoretische Chemie (Wiley-VCH, Weinheim, 2001)
 +
 +==== In a nutshell: how to start ====
 +
 +Beginners should start with Hartree-Fock (basic theory, set up an input for HF, understanding the wf-card input and so on, try out basis sets, inspect orbitals); then one may: \\
 +- either pursue single-reference methods such as MP2, CCSD and variants \\
 +- or progress to MCSCF (MULTI) : wf-card, occ, closed, frozen card etc; then methods such as MRCI \\ 
 +
 +After being familiar with these methods, one may explore more sophisticated tools which rely on them.\\
 +
 +DFT is in many parts similar to Hartree-Fock concerning the input.
 +
 +One should start with a basic input and then gradually increase complexity; it is not a good idea to start with
 +a complicated input and then change input parameters without any knowledge what these parameters are meant for.
 +Break problems into small pieces, and try to solve the smaller problems.
 +
 +A more extended introduction how to use Molpro is in [[quickstart|this section of the manual]].
 +
 +Introductory [[https://www.cond-mat.de/events/correl21/manuscripts/doll.pdf|lecture notes]] and corresponding [[https://www.cond-mat.de/events/correl21/talks/doll.pdf|slides]] from an autumn school in Jülich.
 ==== Miscellaneous ==== ==== Miscellaneous ====
  
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 There is a limit of at most 32 active orbitals which is unlikely to be increased in the near future, see There is a limit of at most 32 active orbitals which is unlikely to be increased in the near future, see
 [[https://www.molpro.net/pipermail/molpro-user/2017-June/006959.html|here]]. An active space of 32 active orbitals is however quite large, and usually smaller active spaces should be sufficient. [[https://www.molpro.net/pipermail/molpro-user/2017-June/006959.html|here]]. An active space of 32 active orbitals is however quite large, and usually smaller active spaces should be sufficient.
 +
 +==== Print all orbital coefficients instead of those which are above the default threshold ====
 +
 +use: ''gthresh,thrprint=0'' see [[https://www.molpro.net/manual/doku.php?id=program_control&s[]=thrprint#global_thresholds_gthresh|here]] 
 +
 +
 ==== molpro: No such file or directory ==== ==== molpro: No such file or directory ====
  
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-==== Print all orbital coefficients instead of those which are above the default threshold ==== 
  
-use: ''gthresh,thrprint=0'' see [[https://www.molpro.net/manual/doku.php?id=program_control&s[]=thrprint#global_thresholds_gthresh|here]]  
 ==== Hardware ==== ==== Hardware ====