[Pw_forum] ambiguous results with vc-relax

Guda Karthik karthik.guda at gmail.com
Wed Aug 4 04:41:42 CEST 2010


I am trying to relax an orthorhombic structure using vc-relax (celldofree -
xyz). I start with a structure which is at a Pressure of -20.5 Kbar and at
the end of the vc-relax I get a structure which is at a pressure of -0.21
Kbar. Surprisingly, the structure at pressure closer to zero is higher in
energy than the original structure by 8 * 10^-4 eV/formula unit. All the
symmetry elements have been conserved during relaxation and the initial and
final structures are the same. I am not able to make sense of this result. I
observe this inconsistency in my B2 structure as well. Please help regarding


Karthik Guda
Graduate Student
Materials Engineering
Purdue University
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