This may help: For some of these transition metal dimers, it is very important to include the semicore states in the valence (ie, the 4p shell for Nb). Otherwise, the bonding distance is too short. This is a problem in the dimer, and usually does not appear in larger clusters or the bulk.
I do not know if this will be the problem with your Nb calculation, but I have seen this in dimers of other TMs nearby in the periodic table. Pablo Ordejon. According to Li-Ger Chen: > > To wheather test the pseudopotential is good. I do bulk test , > dimer test , cluster test on transition metal in bulk ,cluster(atom > numers >8 ), the siesta performed good enough, but in dimer , that is > worse enough > for example, the Nb dimer , experiment reveals that the atom - atom > distance is 2.07 Ang , but in my test, siesta say that is 1.33 Ang > !!!!! > I dont know other DFT simulation program value is why , and someone > say that is coz LDA/GGA form is not good for dimer is some one can > answer me? thanks a lot. > > Liger Chen , National Taiwan > University > -- ---------------------------------------------------------------------------- Dr. Pablo Ordejon Institut de Ciencia de Materials de Barcelona - CSIC Campus de la U.A.B. 08193 Bellaterra, Barcelona (Spain) Phone: +34 93 5801853 Ext. 274 Fax: +34 93 5805729 Email: [EMAIL PROTECTED]
