<div dir="ltr"><div><div>Hi There,<br></div>I am trying to run a transition state calculation using neb.x with methanol C-OH bond breaking in the zeolite micro pore (the 
system is composed of 120 atoms). I have tried relaxing the whole structure with the adsorbate and freezing only the zeolite leaving the adsorbate. I have even tried increasing and decreasing the numbers of processor 
cores from 8-16. I encounter the same error (which is below) regardless .<br> <br><br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br>     task #         0<br>     from rdiaghg : error #       818<br>     S matrix not positive definite<br> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<br></div><div><br><br>What could be the possible cause?<br></div>This is how my input looks like<br><br>BEGIN<br>BEGIN_PATH_INPUT<br>&PATH<br>  restart_mode      = 'from_scratch'<br>  string_method     = 'neb',<br>  nstep_path        = 20,<br>  ds                = 2.D0,<br>  opt_scheme        = "broyden",<br>  num_of_images     = 7,<br>  k_max             = 0.3D0,<br>  k_min             = 0.2D0,<br>  CI_scheme         = "auto",<br>  path_thr          = 0.1D0,<br>/<br>END_PATH_INPUT<br>BEGIN_ENGINE_INPUT<br>&CONTROL<br>  prefix         = "TS1"<br>  outdir         = "./tmp/",<br>  pseudo_dir     = "/home/cbotchway/Cecil",<br>/<br>&SYSTEM<br>  ibrav                  = 0,<br>  nat                    = 120,<br>  ntyp                   = 5,<br>  ecutwfc                = 40.0D0,<br>  ecutrho                = 240.0D0,<br>  nspin                  = 2,<br>  starting_magnetization = 0.5D0,<br>  occupations            = "smearing",<br>  degauss                = 0.03D0,<br>/<br>&ELECTRONS<br>  conv_thr    = 1.D-6,<br>  mixing_beta = 0.2D0,<br>  electron_maxstep =1000000,<br>/<br>&IONS<br>/<br>ATOMIC_SPECIES<br>O    15.99940    O.pbe-van_ak.UPF<br>Si   28.0855    Si.pbe-n-van.UPF<br>Al   26.98154   Al.pbe-n-van.UPF<br>H     1.00794    H.pbe-van_ak.UPF<br clear="all">C    12.0107     C.pbe-van_ak.UPF<br>BEGIN_POSITIONS<br>FIRST_IMAGE<br> <br>Attached to this post is a copy of my input file<br>Any help or advice would be appreciated<br>Thank you in advance<br>-- <br><div class="gmail_signature"><div dir="ltr"><div><div><div>Cecil Huymphrey Botchway<br></div>Mphil. Material Science and Computational Chemistry <br></div>Department of Chemistry<br></div>Kwame Nkrumah University of Science and Technology<br>+23329002372<br></div></div>
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