Dear Forum, I am trying to calculate the bond length of a rhodium dimer in Quantum ESPRESSO. However, I am gaining an unnaturally short bond length of c.a. 1.2 angstrom. I calculated this first as a relaxation, but then carried out scf steps with varying bond lengths (from about 1.0 to 3.0 angstroms) and it gave similar results. I found that this difference in energy was around 10 Ry lower than similar bond lengths. I have tried using different pseudopotentials (PBE, PBEsol and pz), reduced smearing and a higher cut off but they make little difference. I was wondering if there were any issues with my input, or if this is a result of an error in the calculation. Attached is my input file from one of the scf steps:
&CONTROL calculation = "scf", prefix = "QE", pseudo_dir = "/gpfs/bb/nxf093/pseudo", etot_conv_thr= 1.0D-4, forc_conv_thr= 1.0D-3, disk_io = "none", nstep = 500, / &SYSTEM ibrav = 0, nat = 2, ntyp = 1, ecutwfc = 55.D0, occupations = "smearing", smearing = "fd", degauss = 0.020, tot_charge =0, / &ELECTRONS electron_maxstep = 5000, conv_thr = 1.D-5, mixing_beta = 0.6D0, mixing_mode = "local-TF" / &IONS / CELL_PARAMETERS {angstrom} 20.00 0.00 0.00 0.00 20.00 0.00 0.00 0.00 20.00 ATOMIC_SPECIES Rh 102.91 Rh.pbe-spn-kjpaw_psl.0.2.3.UPF ATOMIC_POSITIONS {angstrom} Rh 0.00000 0.00000 0.00000 Rh 2.00000 0.00000 0.00000 K_POINTS {Gamma} Best Wishes, Niall Falconbridge & Jack Davis School of Chemistry University of Birmingham -------------- next part -------------- A non-text attachment was scrubbed... Name: Rhodium Dimer.JPG Type: image/jpeg Size: 120765 bytes Desc: Rhodium Dimer.JPG Url : http://pwscf.org/pipermail/pw_forum/attachments/20140221/e27254ea/attachment.jpe