The full relaxation is only to make the test... There is not a magic number of layers to be freezed in a slab model nor for the correct slab tickness...
On Mon, Dec 5, 2011 at 8:41 AM, Herbert Fruchtl < [email protected]> wrote: > Unless you want to model a thin film in vacuum, you should NEVER let all > atoms relax in a surface calculation. In reality, the lowest layer(s) are > attached to the crystal that's much thicker than your model slab, so you > have to freeze them (or at least one) at the bulk geometry. > > The only possible argument for full relaxation is that you want to prevent > an artificial dipole moment from the fact that the upper surface relaxes > and the lower one doesn't, but even then I would freeze the middle layer. > > Herbert > > > On 05/12/11 10:02, Ary Junior wrote: > >> Hi, >> >> Increase the number of layers and let all atoms to be relaxed... So you >> will >> check "how deep" the relaxation of the atoms from surface will influence >> the >> atoms of the bottom layers... With that test you will have the correct >> slab >> tickness (which will be the half of the converged slab found in the test) >> and >> number of layers to be relaxed in your simulations... >> >> Ary Junior >> Universidade Federal de Juiz de Fora - MG - Brasil >> >> On Sun, Dec 4, 2011 at 4:46 AM, mehzad fatehan <[email protected] >> <mailto:[email protected]>**> wrote: >> >> hi thanks >> energytotal - number of layers ? >> >> >> On Sat, Dec 3, 2011 at 7:31 PM, Ary Junior <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hi, >> >> Do a convergence test and you will find the suitable values for >> the slab >> tickness and number of layers to be relaxed. >> >> Ary Junior >> Universidade Federal de Juiz de Fora - MG - Brasil >> >> >> On Sat, Dec 3, 2011 at 1:58 PM, mehzad fatehan < >> [email protected] >> <mailto:[email protected]>**> wrote: >> >> hi every body >> i am new user >> i want to know Suitablenumber of layers in surface, please >> help me >> >> very thanks >> >> >> >> >> -- >> >> http://lattes.cnpq.br/**8221674673413336<http://lattes.cnpq.br/8221674673413336> >> >> >> >> >> >> -- >> http://lattes.cnpq.br/**8221674673413336<http://lattes.cnpq.br/8221674673413336> >> > > -- > Herbert Fruchtl > Senior Scientific Computing Officer > School of Chemistry, School of Mathematics and Statistics > University of St Andrews > -- > The University of St Andrews is a charity registered in Scotland: > No SC013532 > -- http://lattes.cnpq.br/8221674673413336
