Dear all<br>I am calculated the cohesive energy of Cr using the pseudopotential Cr.pbe-sp-van.UPF. I got is <b>3.63</b> <b>ev/atom</b> as the cohesive energy where as the experimental value is <b>4.1 ev/atom</b>. As i know the GGA pseudopotential should overestimate the cohesive energy value but here it is underestimating. What is the problem? can somebody please help me out.<br>
The magnetic state of the Cr in the bulk is antiferromagnetic at zero kelvin (Neel temperature is ~312 K). For the sake of complete information below are my input files.<br><br><b>Bulk</b><br>&control<br>calculation = 'scf',<br>
restart_mode='from_scratch',<br>outdir='/home/sai/softwares/espresso-4.0.1/workspace/cr_paramagnetic/temp',<br>prefix='chromium'<br>pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',<br>
/<br>&system<br>ibrav=1<br>celldm(1)=5.250000,<br>nat=2,<br>ntyp=2,<br>ecutwfc=60,<br>ecutrho=600,<br>occupations='smearing',<br>smearing='mp',<br>degauss=0.010000<br>nspin=2<br>starting_magnetization(1)=0.5<br>
starting_magnetization(2)=-0.5<br>/<br>&electrons<br>conv_thr=1.D-8,<br>diagonalization='david',<br>mixing_mode='plain',<br>mixing_beta= 0.7<br>/<br>ATOMIC_SPECIES<br>Cr1 51.9961 Cr.pbe-sp-van.UPF<br>
Cr2 51.9961 Cr.pbe-sp-van.UPF<br>ATOMIC_POSITIONS (crystal)<br>Cr1 0.00 0.00 0.00<br>Cr2 0.5 0.5 0.5<br>K_POINTS {automatic}<br>10 10 10 0 0 0<br><br><b>Isolated</b><br clear="all">&control<br>calculation = 'scf',<br>
restart_mode='from_scratch',<br>outdir='/home/sai/softwares/espresso-4.0.1/workspace/cr_paramagnetic/temp',<br>prefix='chromium'<br>pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',<br>
/<br>&system<br>ibrav=1<br>celldm(1)=15,<br>nat=1,<br>ntyp=1,<br>ecutwfc=60,<br>ecutrho=600,<br>occupations='fixed',<br>tot_magnetization=6<br>nspin=2<br>nosym=.true.,<br>/<br>&electrons<br>conv_thr=1.D-8,<br>
diagonalization='david',<br>mixing_mode='plain',<br>mixing_beta= 0.7<br>/<br>ATOMIC_SPECIES<br>Cr 51.9961 Cr.pbe-sp-van.UPF<br>ATOMIC_POSITIONS (crystal)<br>Cr 0.00 0.00 0.00<br>K_POINTS {automatic}<br>1 1 1 0 0 0<br>
-- <br>U.Saibabu<br>PhD student,<br>Deformation mechanisms modeling group,<br>Materials engineering department,<br>IISc Bangalore,<br>India.<br><br>