===== Lattice parameter ===== In this section, we explain how to optimize the lattice parameter of Ci bulk fcc structure. The fcc structure is characterized by single distinct atom per unit cell with relative coordinates ''(0 ,0 ,0)'' . The lattice vector is defined in the relative coordinates ''alat*(1/4, 1/4, 1/4)''. Detail description of the diamond structure can be found [[http://en.wikipedia.org/wiki/Cubic_crystal_system|elsewhere]]. There is an elegant way to rescale atomic coordinates, lattice vector and k-points by only one parameter **''rescal''** defined in the section **''&OPTIONS''**. Our input atomic coordinates written in **''Cu_bulk.bas''** look like: 1 29 0.00000 0.00000 0.00000 The lattice vector is defined in **''Cu_bulk.lvs''** file: 0.70711 0.00000 0.00000 0.35355 0.61237 0.00000 0.35355 0.20412 0.57735 The k-points 8x8x8 Monkhorst-Pack grid can be by Oh symmetry reduced into 128 k-points. They are in **''Cu_bulk.kpts''** file: 128 -1.07541645 -0.62089056 -0.10467514 0.00781250 -1.07541645 -0.62089056 -0.07476795 0.00781250 -1.07541645 -0.62089056 -0.04486077 0.00781250 -1.07541645 -0.62089056 -0.01495359 0.00781250 -1.07541645 -0.26609597 -0.10467514 0.00781250 -1.07541645 -0.26609597 -0.07476795 0.00781250 -1.07541645 -0.26609597 -0.04486077 0.00781250 -1.07541645 -0.26609597 -0.01495359 0.00781250 -1.07541645 0.08869865 -0.10467514 0.00781250 -1.07541645 0.08869865 -0.07476795 0.00781250 -1.07541645 0.08869865 -0.04486077 0.00781250 -1.07541645 0.08869865 -0.01495359 0.00781250 -1.07541645 0.44349325 -0.10467514 0.00781250 -1.07541645 0.44349325 -0.07476795 0.00781250 -1.07541645 0.44349325 -0.04486077 0.00781250 -1.07541645 0.44349325 -0.01495359 0.00781250 -1.07541645 0.79828787 -0.10467514 0.00781250 -1.07541645 0.79828787 -0.07476795 0.00781250 -1.07541645 0.79828787 -0.04486077 0.00781250 -1.07541645 0.79828787 -0.01495359 0.00781250 1.38267840 -0.26609593 -0.10467514 0.00781250 1.38267840 -0.26609593 -0.07476795 0.00781250 1.38267840 -0.26609593 -0.04486077 0.00781250 1.38267840 -0.26609593 -0.01495359 0.00781250 1.38267840 0.08869869 -0.10467514 0.00781250 1.38267840 0.08869869 -0.07476795 0.00781250 1.38267840 0.08869869 -0.04486077 0.00781250 1.38267840 0.08869869 -0.01495359 0.00781250 -1.07541645 -0.97568511 -0.10467514 0.00781250 -1.07541645 -0.97568511 -0.07476795 0.00781250 -1.07541645 -0.97568511 -0.04486077 0.00781250 -1.07541645 -0.97568511 -0.01495359 0.00781250 -0.76815462 -0.79828787 -0.10467514 0.00781250 -0.76815462 -0.79828787 -0.07476795 0.00781250 -0.76815462 -0.79828787 -0.04486077 0.00781250 -0.76815462 -0.79828787 -0.01495359 0.00781250 -0.76815462 -0.44349325 -0.10467514 0.00781250 -0.76815462 -0.44349325 -0.07476795 0.00781250 -0.76815462 -0.44349325 -0.04486077 0.00781250 -0.76815462 -0.44349325 -0.01495359 0.00781250 -0.76815462 -0.08869865 -0.10467514 0.00781250 -0.76815462 -0.08869865 -0.07476795 0.00781250 -0.76815462 -0.08869865 -0.04486077 0.00781250 -0.76815462 -0.08869865 -0.01495359 0.00781250 -0.76815462 0.26609597 -0.10467514 0.00781250 -0.76815462 0.26609597 -0.07476795 0.00781250 -0.76815462 0.26609597 -0.04486077 0.00781250 -0.76815462 0.26609597 -0.01495359 0.00781250 -0.76815462 0.62089056 -0.10467514 0.00781250 -0.76815462 0.62089056 -0.07476795 0.00781250 -0.76815462 0.62089056 -0.04486077 0.00781250 -0.76815462 0.62089056 -0.01495359 0.00781250 -0.76815462 0.97568518 -0.10467514 0.00781250 -0.76815462 0.97568518 -0.07476795 0.00781250 -0.76815462 0.97568518 -0.04486077 0.00781250 -0.76815462 0.97568518 -0.01495359 0.00781250 -0.76815462 1.33047974 -0.10467514 0.00781250 -0.76815462 1.33047974 -0.07476795 0.00781250 -0.76815462 1.33047974 -0.04486077 0.00781250 -0.76815462 1.33047974 -0.01495359 0.00781250 -0.76815462 -1.15308248 0.61309722 0.00781250 -0.76815462 -1.15308248 0.64300440 0.00781250 -0.76815462 -1.15308248 0.67291158 0.00781250 -0.76815462 -1.15308248 0.70281876 0.00781250 -0.46089280 -0.97568518 -0.10467514 0.00781250 -0.46089280 -0.97568518 -0.07476795 0.00781250 -0.46089280 -0.97568518 -0.04486077 0.00781250 -0.46089280 -0.97568518 -0.01495359 0.00781250 -0.46089280 -0.62089056 -0.10467514 0.00781250 -0.46089280 -0.62089056 -0.07476795 0.00781250 -0.46089280 -0.62089056 -0.04486077 0.00781250 -0.46089280 -0.62089056 -0.01495359 0.00781250 -0.46089280 -0.26609597 -0.10467514 0.00781250 -0.46089280 -0.26609597 -0.07476795 0.00781250 -0.46089280 -0.26609597 -0.04486077 0.00781250 -0.46089280 -0.26609597 -0.01495359 0.00781250 -0.46089280 0.08869865 -0.10467514 0.00781250 -0.46089280 0.08869865 -0.07476795 0.00781250 -0.46089280 0.08869865 -0.04486077 0.00781250 -0.46089280 0.08869865 -0.01495359 0.00781250 -0.46089280 0.44349325 -0.10467514 0.00781250 -0.46089280 0.44349325 -0.07476795 0.00781250 -0.46089280 0.44349325 -0.04486077 0.00781250 -0.46089280 0.44349325 -0.01495359 0.00781250 -0.46089280 0.79828787 -0.10467514 0.00781250 -0.46089280 0.79828787 -0.07476795 0.00781250 -0.46089280 0.79828787 -0.04486077 0.00781250 -0.46089280 0.79828787 -0.01495359 0.00781250 -0.46089280 1.15308249 -0.10467514 0.00781250 -0.46089280 1.15308249 -0.07476795 0.00781250 -0.46089280 1.15308249 -0.04486077 0.00781250 -0.46089280 1.15308249 -0.01495359 0.00781250 -0.46089280 -1.33047973 0.61309722 0.00781250 -0.46089280 -1.33047973 0.64300440 0.00781250 -0.46089280 -1.33047973 0.67291158 0.00781250 -0.46089280 -1.33047973 0.70281876 0.00781250 -0.15363093 -1.15308249 -0.10467514 0.00781250 -0.15363093 -1.15308249 -0.07476795 0.00781250 -0.15363093 -1.15308249 -0.04486077 0.00781250 -0.15363093 -1.15308249 -0.01495359 0.00781250 -0.15363093 -0.79828787 -0.10467514 0.00781250 -0.15363093 -0.79828787 -0.07476795 0.00781250 -0.15363093 -0.79828787 -0.04486077 0.00781250 -0.15363093 -0.79828787 -0.01495359 0.00781250 -0.15363093 -0.44349325 -0.10467514 0.00781250 -0.15363093 -0.44349325 -0.07476795 0.00781250 -0.15363093 -0.44349325 -0.04486077 0.00781250 -0.15363093 -0.44349325 -0.01495359 0.00781250 -0.15363093 -0.08869865 -0.10467514 0.00781250 -0.15363093 -0.08869865 -0.07476795 0.00781250 -0.15363093 -0.08869865 -0.04486077 0.00781250 -0.15363093 -0.08869865 -0.01495359 0.00781250 -0.15363093 0.26609597 -0.10467514 0.00781250 -0.15363093 0.26609597 -0.07476795 0.00781250 -0.15363093 0.26609597 -0.04486077 0.00781250 -0.15363093 0.26609597 -0.01495359 0.00781250 -0.15363093 0.62089056 -0.10467514 0.00781250 -0.15363093 0.62089056 -0.07476795 0.00781250 -0.15363093 0.62089056 -0.04486077 0.00781250 -0.15363093 0.62089056 -0.01495359 0.00781250 -0.15363093 0.97568518 -0.10467514 0.00781250 -0.15363093 0.97568518 -0.07476795 0.00781250 -0.15363093 0.97568518 -0.04486077 0.00781250 -0.15363093 0.97568518 -0.01495359 0.00781250 -0.15363093 1.33047974 -0.10467514 0.00781250 -0.15363093 1.33047974 -0.07476795 0.00781250 -0.15363093 1.33047974 -0.04486077 0.00781250 -0.15363093 1.33047974 -0.01495359 0.00781250 The **''Fireball.sample''** file from which fireball.in will be created looks like this: &OPTION basisfile = Cu_bulk.bas lvsfile = Cu_bulk.lvs kptpreference = Cu_bulk.kpts nstepf = 1 rescal = AAA &END And finally the running script named eg. fireball.sh is here (please note, that in you directory there has to be a file called runTG.com, which obtains path to the fireball.k.x executable, or the executable itselves): alat="3.21 3.22 3.23 3.24 3.25 3.26 3.27 3.28 3.29 3.30 3.31 3.32 3.33 3.34 3.35 3.36 3.37 3.38 3.39" for i in $alat; do echo $i mkdir $i lattice="`echo $i`"; sed "s/AAA/$lattice/g" fireball.sample > fireball.in; ./runTG.com > a-$i.out en=`grep "etot/atom" a-$i.out | cut -b50-65` echo $i $en >> energy.dat mv CHARGES $i/ mv a-$i.out $i/ done By simple plotting with gnuplot: plot "energy.dat" w lp {{:energy.png|}} , you'll obtain, that the optimized lattice constant is 3.3 Angstrom. (The experimental is 3.614 Angstrom.)