I calculated some time ago some bulk properties of Vanadium using the same PP you used and I obtained the following:
Isolated: -27.260Ry Bulk: -27.666Ry (a=5.675) Cohesive energy: 5.52eV/atom Predicted equilibrium lat. param.: 3.00angstrom (Experimental is 3.03, I think) The equilibrium values are well reproduced. I don't remember (I don't have the inputs with me) exactly all the details, but the difference is probably related to the fact that spin has to be included for the isolated atom, as already mentioned by other PW users. All best. P.S: Sorry for sending two e-mails. F?bio Negreiros Ribeiro PHd student - Departamento de F?sica - Universidade Federal de Minas Gerais Belo Horizonte - MG - Brazil -----Original Message----- From: udayagiri sai babu <[email protected]> To: pw_forum at pwscf.org Sent: Mon, Aug 31, 2009 8:37 pm Subject: [Pw_forum] calculating cohesive energy Hi all i am claculating cohesive energy of V using pwscf but i got -8.15 ev/atom against an experimental value of 5.3 ev/atom which is almost 50% off can anybody say what is going wrong with the calculation. the method i used is calculate the total energy of a bcc crystal with 1 atom and deduct the energy of isolated atom from it. the following input files are for finding the total energy for isolated atom and the atom in the crystal. Please tell me if my methodology is wrong. cohesive energy=E per atom (in the crystal)-E per atom (isolated) inpu t file for finding the total energy of an isolated atom &control calculation = 'scf', restart_mode='from_scratch', outdir='/home/sai/temp', prefix='vanadium' pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/', tstress = .TRUE., tprnfor = .TRUE., / &system ibrav=1 celldm(1)=30, nat=1, ntyp=1 ecutwfc=25, ecutrho=100, occupations='smearing', smearing='mv', degauss=0.010000 / &electrons conv_thr=1.D-8, diagonalization='david', ? mixing_mode='plain', mixing_beta= 0.3 / ATOMIC_SPECIES V? 50.9415? V.pbe-n-van.UPF ATOMIC_POSITIONS (crystal) V?????? 0.00000000????? 0.00000000????? 0.00000000 K_POINTS {automatic} 1 1 1 0 0 0 input file for finding the total energy of the atom in the crystal &control calculation = 'scf', restart_mode='from_scratch', outdir='/home/sai/temp', prefix='vanadium' pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/', tstress = .TRUE., tprnfor = .TRUE., / &system ibrav=3 celldm(1)=5.654, nat=1, ntyp=1 ecutwfc=25, ecutrho=100, occupations='smearing', smearing='mv', degauss=0.010000 / &electrons conv_thr=1.D-8, diagonalization='david', mixing_mode='plain', mixing_beta= 0.3 / ATOMIC_SPECIES V? 50.9415? V.pbe-n-van.UPF ATOMIC_POSITIONS (crystal) V?????? 0.00000000????? 0.00000000?????200.00000000 K_POINTS {aut omatic} 8 8 8 0 0 0_______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
