Stefano Baroni wrote: > parameters along energy derivatives (forces and stress). When the ground > state is nondegenerate, energy derivatives have the same symmetry as the > the geometry of the system.
Please Stefano help me to understand this point, which is not clear to me. If the ground state is degenerate (you meant degenerate at a fixed external potential, i.e. fixed atomic geometry, am I right?) you could reach a lower energy by lowering the symmetry: do you think this is possible in practical calculations. I thought that you could only end up in a configuration with higher symmetry than the starting one, not lower. From the theoretical point of view, is it correct to apply the standard formulation of HK theorem to a system with degenerate GS (is the HK mapping still valid?). Gabriele > > --- > Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste > http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) / > stefanobaroni (skype) -- o ------------------------------------------------ o | Gabriele Sclauzero, PhD Student | | c/o: SISSA & CNR-INFM Democritos, | | via Beirut 2-4, 34014 Trieste (Italy) | | email: sclauzer at sissa.it | | phone: +39 040 3787 511 | | skype: gurlonotturno | o ------------------------------------------------ o
