\contentsline {section}{\numberline {1}Introduction}{2}{section.1}
\contentsline {subsection}{\numberline {1.1}What can \texttt {PWscf}\ do}{2}{subsection.1.1}
\contentsline {subsection}{\numberline {1.2}People}{2}{subsection.1.2}
\contentsline {subsection}{\numberline {1.3}Terms of use}{4}{subsection.1.3}
\contentsline {section}{\numberline {2}Compilation}{4}{section.2}
\contentsline {section}{\numberline {3}Using \texttt {PWscf}}{6}{section.3}
\contentsline {subsection}{\numberline {3.1}Input data}{6}{subsection.3.1}
\contentsline {subsection}{\numberline {3.2}Data files}{7}{subsection.3.2}
\contentsline {subsection}{\numberline {3.3}Electronic structure calculations}{7}{subsection.3.3}
\contentsline {paragraph}{Single-point (fixed-ion) SCF calculation}{7}{section*.2}
\contentsline {paragraph}{Band structure calculation}{7}{section*.3}
\contentsline {paragraph}{Noncollinear magnetization, spin-orbit interactions}{8}{section*.4}
\contentsline {paragraph}{DFT+U}{8}{section*.5}
\contentsline {paragraph}{Dispersion Interactions (DFT-D)}{8}{section*.6}
\contentsline {paragraph}{Hartree-Fock and Hybrid functionals}{8}{section*.7}
\contentsline {paragraph}{Dispersion interaction with non-local functional (vdW-DF)}{9}{section*.8}
\contentsline {paragraph}{Polarization via Berry Phase}{9}{section*.9}
\contentsline {paragraph}{Finite electric fields}{9}{section*.10}
\contentsline {paragraph}{Orbital magnetization}{9}{section*.11}
\contentsline {subsection}{\numberline {3.4}Optimization and dynamics}{9}{subsection.3.4}
\contentsline {paragraph}{Structural optimization}{9}{section*.12}
\contentsline {paragraph}{Molecular Dynamics}{9}{section*.13}
\contentsline {paragraph}{Free-energy surface calculations}{9}{section*.14}
\contentsline {paragraph}{Variable-cell optimization}{9}{section*.15}
\contentsline {paragraph}{Variable-cell molecular dynamics}{10}{section*.16}
\contentsline {subsection}{\numberline {3.5}Direct interface with \texttt {CASINO}}{10}{subsection.3.5}
\contentsline {paragraph}{Practicalities}{10}{section*.17}
\contentsline {paragraph}{How to generate \texttt {xwfn.data} files with \texttt {PWscf}}{11}{section*.18}
\contentsline {subsection}{\numberline {3.6}Socket interface with i-PI}{12}{subsection.3.6}
\contentsline {paragraph}{Practicalities}{12}{section*.19}
\contentsline {paragraph}{How to use the i-PI inteface}{12}{section*.20}
\contentsline {section}{\numberline {4}Performances}{13}{section.4}
\contentsline {subsection}{\numberline {4.1}Execution time}{13}{subsection.4.1}
\contentsline {subsection}{\numberline {4.2}Memory requirements}{14}{subsection.4.2}
\contentsline {subsection}{\numberline {4.3}File space requirements}{14}{subsection.4.3}
\contentsline {subsection}{\numberline {4.4}Parallelization issues}{15}{subsection.4.4}
\contentsline {subsection}{\numberline {4.5}Understanding the time report}{16}{subsection.4.5}
\contentsline {subsubsection}{\numberline {4.5.1}Serial execution}{16}{subsubsection.4.5.1}
\contentsline {subsubsection}{\numberline {4.5.2}Parallel execution}{17}{subsubsection.4.5.2}
\contentsline {paragraph}{ Quick estimate of parallelization parameters}{17}{section*.21}
\contentsline {paragraph}{Typical symptoms of bad/inadequate parallelization}{18}{section*.22}
\contentsline {subsection}{\numberline {4.6}Restarting}{18}{subsection.4.6}
\contentsline {subsubsection}{\numberline {4.6.1}Signal trapping (experimental!)}{19}{subsubsection.4.6.1}
\contentsline {section}{\numberline {5}Troubleshooting}{19}{section.5}
\contentsline {paragraph}{pw.x says 'error while loading shared libraries' or 'cannot open shared object file' and does not start}{19}{section*.23}
\contentsline {paragraph}{errors in examples with parallel execution}{19}{section*.24}
\contentsline {paragraph}{pw.x prints the first few lines and then nothing happens (parallel execution)}{20}{section*.25}
\contentsline {paragraph}{pw.x stops with error while reading data}{20}{section*.26}
\contentsline {paragraph}{pw.x mumbles something like {\em cannot recover} or {\em error reading recover file}}{20}{section*.27}
\contentsline {paragraph}{pw.x stops with {\em inconsistent DFT} error}{20}{section*.28}
\contentsline {paragraph}{pw.x stops with error in cdiaghg or rdiaghg}{20}{section*.29}
\contentsline {paragraph}{pw.x crashes with no error message at all}{21}{section*.30}
\contentsline {paragraph}{pw.x crashes with {\em segmentation fault} or similarly obscure messages}{21}{section*.31}
\contentsline {paragraph}{pw.x works for simple systems, but not for large systems or whenever more RAM is needed}{21}{section*.32}
\contentsline {paragraph}{pw.x crashes with {\em error in davcio}}{22}{section*.33}
\contentsline {paragraph}{pw.x crashes in parallel execution with an obscure message related to MPI errors}{22}{section*.34}
\contentsline {paragraph}{pw.x stops with error message {\em the system is metallic, specify occupations}}{22}{section*.35}
\contentsline {paragraph}{pw.x stops with {\em internal error: cannot bracket Ef}}{22}{section*.36}
\contentsline {paragraph}{pw.x yields {\em internal error: cannot bracket Ef} message but does not stop}{23}{section*.37}
\contentsline {paragraph}{pw.x runs but nothing happens}{23}{section*.38}
\contentsline {paragraph}{pw.x yields weird results}{23}{section*.39}
\contentsline {paragraph}{FFT grid is machine-dependent}{23}{section*.40}
\contentsline {paragraph}{pw.x does not find all the symmetries you expected}{24}{section*.41}
\contentsline {paragraph}{{\em Warning: symmetry operation \# N not allowed}}{24}{section*.42}
\contentsline {paragraph}{Self-consistency is slow or does not converge at all}{24}{section*.43}
\contentsline {paragraph}{I do not get the same results in different machines!}{25}{section*.44}
\contentsline {paragraph}{Execution time is time-dependent!}{25}{section*.45}
\contentsline {paragraph}{{\em Warning : N eigenvectors not converged}}{25}{section*.46}
\contentsline {paragraph}{{\em Warning : negative or imaginary charge...}, or {\em ...core charge ...}, or {\em npt with rhoup$<0$...} or {\em rho dw$<0$...}}{25}{section*.47}
\contentsline {paragraph}{Structural optimization is slow or does not converge or ends with a mysterious bfgs error}{26}{section*.48}
\contentsline {paragraph}{pw.x stops during variable-cell optimization in checkallsym with {\em non orthogonal operation} error}{26}{section*.49}
\contentsline {subsection}{\numberline {5.1}Compilation problems with \texttt {PLUMED}}{26}{subsection.5.1}
\contentsline {paragraph}{xlc compiler}{26}{section*.50}
\contentsline {paragraph}{Calling C from fortran}{27}{section*.51}