1 2This example shows how to use pw.x to calculate the total energy 3and the band structure of four simple systems: Si, Al, Cu, Ni . 4 5The calculation proceeds as follows (for the meaning of the cited input 6variables see the appropriate INPUT_* file) 7 81) make a self-consistent calculation for Si (input=si.scf.{david,cg}.in, 9 output=si.scf.{david,cg}.out). The number of computed bands is internally 10 computed as half the number of electrons in the unit cell 11 (4 in this case). 12 132) make a band structure calculation for Si (input=si.band.{david,cg}.in, 14 output=si.band.{david,cg}). 15 The variable nbnd is explicitly set = 8 so that the 4 valence bands 16 and the first 4 conduction bands are calculated. 17 The list of k points given in input is the list of point where the 18 bands are computed, the k-point weight is arbitrary and is not used. 19 203) make a self-consistent calculation for Al (input=al.scf.{david,cg}.in, 21 output=al.scf.{david,cg}.out). 22 Aluminum is a metal : the smearing technique is used for the 23 calculation of the Fermi energy (a value for the broadening 24 degauss is provided). 25 The number of bands is set to a value somehow larger that half 26 the number of electrons in the cell (this is a quantity to keep under 27 control and provide explicitly if the default value is too small). 28 Marzari-Vanderbilt 'cold smearing' is used. 29 304) make a band structure calculation for Al. (input=al.band.{david,cg}.in, 31 output=al.band.{david,cg}.out). 32 The variable nbnd is explicitly set = 8. 33 The list of k points given in input is the list of point where the 34 bands are computed, the k-point weight is arbitrary and is not used. 35 365) make a self-consistent calculation for Cu (input=cu.scf.{david,cg}.in, 37 output=cu.scf.{david,cg}.out). 38 Copper is also a metal. Simple Gaussian smearing is used 39 for the calculation of the Fermi energy. K-points are automatically 40 generated. 41 426) make a band structure calculation for Cu (input=cu.band.{david,cg}.in, 43 output=cu.band.{david,cg}.out). 44 The variable nbnd is explicitly set = 8. 45 The list of k points given in input is the list of point where the 46 bands are computed, the k-point weight is arbitrary and is not used. 47 487) make a self-consistent calculation for Ni (input=ni.scf.{david,cg}.in, 49 output=ni.scf.{david,cg}.out). 50 Nickel is a magnetic metal. A local-spin-density calculation is 51 performed by specifying nspin=2 and an initial guess for the 52 magnetization of each atomic species. This initial guess is used to 53 build spin-up and spin-down starting charges from superposition of 54 atomic charges. Methfessel-Paxton smearing of order one is used. 55 568) make a band structure calculation for Ni (input=ni.band.{david,cg}.in, 57 output=ni.band.{david,cg}.out). 58 59The above is done both for Davidson diagonalization (suffix 60'david') and for Conjugate-gradient style diagonalization ('cg'). 61The code is tolerant about the presence of unnecessary information 62in the namelists so that it is not necessary to remove them from the 63input when editing the scf input to get the one for a nscf run. 64 65