Dear Ravi You are using a *very* small cell. Try to calculate the H concentration. It will probably be a huge, unphysical value. Moreover, the localized H (probably a covalent hydride H- in a metal) is strongly interacting with its periodically replicated images, which are at a very short distance. Try to use a larger supercell and see how much the results change. HTH Giuseppe
On Friday, January 30, 2015 05:13:18 PM Ravi Kiran wrote: > Hi, > > I am using neb to calculate activation energy of hydrogen in unit cell of > nickel. I have placed hydrogen in octahedral position and I am moving it to > another octahedral position as shown below. My question is whether neb can > calculates transition state which is tetrahedral site?. I have used a > path_thr of 0.01eV with 7 images. I have calculated the activation energy > which I am getting is 1.05 eV as shown in output, whereas the experiments > indicate 0.42. > > *input * > > FIRST_IMAGE > ATOMIC_POSITIONS crystal > Ni 0 0 0 > Ni 0 0.5 0.5 > Ni 0.5 0 0.5 > Ni 0.5 0.5 0 > H 0.5 0.5 0.5 > LAST_IMAGE > ATOMIC_POSITIONS crystal > Ni 0 0 0 > Ni 0 0.5 0.5 > Ni 0.5 0 0.5 > Ni 0.5 0.5 0 > H 0.0 0.5 0.0 > END_POSITIONS > *output* > ------------------------------ iteration 56 ------------------------------ > > tcpu = 6675.4 self-consistency for image 1 > tcpu = 6683.4 self-consistency for image 2 > tcpu = 6764.1 self-consistency for image 3 > tcpu = 6846.9 self-consistency for image 4 > tcpu = 6948.8 self-consistency for image 5 > tcpu = 7031.7 self-consistency for image 6 > tcpu = 7113.1 self-consistency for image 7 > > activation energy (->) = 1.024248 eV > activation energy (<-) = 1.024248 eV > > image energy (eV) error (eV/A) frozen > > 1 -4690.3920838 0.000000 F > 2 -4690.3237895 0.006072 F > 3 -4689.7348781 0.005158 F > 4 -4689.3678358 0.006904 F > 5 -4689.7349752 0.004005 F > 6 -4690.3237535 0.006484 F > 7 -4690.3920838 0.000000 F > > path length = 5.711 bohr > inter-image distance = 0.952 bohr ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ègaux en droits. Les distinctions sociales ne peuvent être fondèes que sur l'utilitè commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libertè, la propriètè, la sùretè et la rèsistance à l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <[email protected]> http://www.ism.cnr.it/english/staff/mattiolig ResearcherID: F-6308-2012 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
