Did you check your k-point sampling? -------------------------------------------------- Duy Le PhD Student Department of Physics University of Central Florida.
"Men don't need hand to do things" On Wed, Mar 2, 2011 at 5:58 PM, Krukau, Aliaksandr <akrukau at indiana.edu> wrote: > ? Dear QE users, > ? ?I apologize if my question seems stupid to you. I am a complete QE newbie > and could not find any answer in the tutorials. > ? ?I am trying to find equilibrium lattice constant for copper with PBE > and ultrasoft pseudopotentials. I ran scf calculations for face-centered cubic > unit cell for a number of lattice constants: > Lattice constant 6.65 a.u. ! ? ?total energy ? ? ? ? ? ? ?= > -121.62734203 Ry > Lattice constant 6.66 a.u. ! ? ?total energy ? ? ? ? ? ? ?= > -121.62735421 Ry > Lattice constant 6.67 a.u. ! ? ?total energy ? ? ? ? ? ? ?= > -121.62734651 Ry > Lattice constant 6.65 a.u. ! ? ?total energy ? ? ? ? ? ? ?= > -121.62731956 Ry > ? ?The minimum total energy is for the lattice constant 6.66 a.u. > But this value drastically differs from the published PBE value of 6.86 a.u. > (Phys. Rev. B, vol. 77, 05414 (2008), Table II). It also differs from > the experimental value of 6.83 a.u. I attach the input file that I used > for lattice constant 6.66 a.u. below the signature. > ? ?Why is equilibrium lattice constant so low? > Best regards, > Alex Krukau, > Indiana University > > ------------------------------------------------------ > &control > ? ?calculation='scf' > ? ?pseudo_dir = '~/espresso-4.2.1/pseudo/ADDITIONAL', > / > &system > ? ?ibrav = 2, > ? ?celldm(1) = 6.66, > ? ?nat= 1, > ? ?ntyp= 1, > ? ?ecutwfc = 120.0, > ? ?ecutrho = 1000.0 > ? ?occupations='smearing', smearing='marzari-vanderbilt', degauss=0.01 > / > &electrons > ? ?conv_thr=0.0000001 > / > ATOMIC_SPECIES > Cu ?63.546 Cu.pbe-n-van_ak.UPF > ATOMIC_POSITIONS > Cu 0.0 0.0 0.0 ? ?1 ? 1 ? 1 > K_POINTS automatic > 12 12 1 0 0 0 > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
