Dear All, At present I am trying to calculate the phonon modes of double perovskite Ba2SmTaO6 having a cubic Fm3m structure. The detailed input of the vc-relax file is provided below (and also attached alongwith).
&CONTROL calculation='vc-relax', restart_mode='from_scratch', prefix='BST' pseudo_dir = '/home/saswata/espresso/potentials/', outdir='./' tstress=.true. tprnfor=.true. verbosity='high' wf_collect=.true. nstep=200 etot_conv_thr=1.0D-7 forc_conv_thr=1.0D-4 disk_io='default' / &SYSTEM ibrav = 2, celldm(1) =16.0208, nat = 10, ntyp= 4, ecutwfc = 80.0, ecutrho=800, occupations='smearing', smearing='gaussian', degauss=0.02, nspin=2, starting_magnetization(2)=0.4, lda_plus_u=.true., Hubbard_U(2)=7.0, / &ELECTRONS diagonalization='david', mixing_mode='plain', mixing_beta = 0.7D0 conv_thr = 1.0D-9 electron_maxstep=200 / &IONS ion_dynamics='bfgs' upscale=10D0 trust_radius_max=1.0D0 trust_radius_min=1.0D-5 trust_radius_ini=0.5D0 w_1=0.01D0 w_2=0.5D0 / &CELL cell_dynamics='bfgs', press=0.0, cell_factor=2.5D0, press_conv_thr=0.2, / ATOMIC_SPECIES Ba 137.327 Ba.pbe-mt_fhi.UPF Sm 150.360 Sm.pbe-mt_fhi.UPF Ta 180.94788 Ta.pbe-mt_fhi.UPF O 15.9994 O.pbe-mt_fhi.UPF ATOMIC_POSITIONS crystal Ba 0.25 0.25 0.25 Ba 0.75 0.75 0.75 Sm 0.00 0.00 0.00 Ta 0.50 0.50 0.50 O 0.264 0.00 0.00 O 0.736 0.00 0.00 O 0.00 0.264 0.00 O 0.00 0.736 0.00 O 0.00 0.00 0.264 O 0.00 0.00 0.736 K_POINTS automatic 4 4 4 1 1 1 I specifically have two questions regarding the output of this calculation 1. The structural relaxation occurs but with a pressure value of P=-13.71. What is the significance of this negative pressure? 2. The phonon calculation terminates with an error message 'LDA+U is not implemented in phonon'. Is there any other way to go about with this calculation in the existing QE versions? Thanking you in advance and awaiting a reply eagerly, Saswata Halder. Senior Research Fellow Bose Institute.
bst.relaxcell.in
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