Energy vs. lattice constant

The calculation of Energy vs. lattice constant is supported by the following keywords:

  MD.Type                     EvsLC      #
  MD.EvsLC.Step                0.4       # default=0.4%
  MD.maxIter                   32        # default=1
  MD.EvsLC.flag              1 1 1       # default=1 1 1 
  # (0: fixed, 1:expansion, -1:contraction)

When 'MD.Type' is set to 'EvsLC', the total energy is calculated step by step by changing unit cell vectors, a, b, and c. The change of unit cell vectors is done uniformly by expanding them by a percentage, where the reference is the initial vectors, specified with 'MD.EvsLC.Step'. The number of steps is specified by the keyword 'MD.maxIter'. If you want to fix some of lattice vectors, the keyword 'MD.EvsLC.flag' is available, where the default setting is '1 1 1' corresponding to the uniform expansion of a-, b-, c-axes, respectively. The flag '0' means no change of the corresponding axis, and '-1' the uniform contraction. After the calculation, you will obtain a file 'System.Name.EvsLC', where 'System.Name' is 'System.Name'. The columns in the file 'System.Name.EvsLC' are arranged in order of $a_x$, $a_y$, $a_z$, $b_x$, $b_y$, $b_z$, $c_x$, $c_y$, $c_z$ in Å, and the total energy in Hartree, where $a(b,c)_x$, $a(b,c)_y$, and $a(b,c)_z$ are x-, y-, and z-coordinates of the a(b,c) vector, respectively. As an example, calculation of Energy vs. lattice for the fcc Mn bulk is shown in Fig. 53, where the equilibrium lattice constant and bulk modulus were evaluated by fitting the data to the Murnaghan equation of state with a code 'murn.f' provided on the web site [101].

Figure 53: Total energy vs. lattice constant for the fcc Mn bulk calculated by the keyword 'EvsLC'. The input file used for the calculation is 'Mnfcc-EvsLC.dat' in the directory 'work'.