Execution of SCFC

The execution of SCFC requires a data set with total and projected state densities and number-of-states functions as generated by DDNS and stored in DOS/YY/B. An example of the additional input, which consists of control variables and the atomic charge densities, is shown in Table 9.7. 

In the second line EXCHF is the Slater Xa factor, but since IXCH = 0 this is not used. The next four numbers are the energy increments in Rydbergs used in the first two iterations to evaluate the energy derivatives. As mentioned in the paragraph about Step 3 in Sect.9.6, later iterations use a fraction of the relevant bandwidth. Further, RKEY = 1 R1 indicates that the entries in Line 4 are the radii in atomic units rather than a percentage of the radius used in the original band calculation. 

In the third line IBLX = 0 means that the charge density for the N + l th iteration will be BLXB = 0.8 times that of iteration N-l plus 0.2 times that of iteration N. If IBLX = 1, the mixing starts at BLXA = 0.9 and decreases in steps of DBLX = 0.01. In most applications a mixing of 0.8 will work, but in difficult cases it should be as high as 0.95 - 0.99. The symptoms of too small a mixing are that the Fermi level, the magnetic moment 254 

The fourth line contains the NW Wigner-Seitz radii in atomic units since RKEY = 1 R1. If RKEY is different from R, Line 4 should contain the desired percentage increase in the current Wigner-Seitz radius over that of the original radius. 

In the fifth line, MT(IT) = 1 indicates that there is only one atom of type IT in the unit cell. For an alloy such as Pt Sn this line should have contained the numbers 3 and 1. 

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Upon completion, the programme will print the four standard potential parameters per z9 some other potential parameters, e.g. masses and band edges, zeroth-, first-, and second-order moments of the state density, and partial and total pressures. If the potential parameters in the original run of LMTO have been suitably chosen, one will have a reasonably converged result after just one execution of SCFC. If this is not the case, one must use the output potential parameters to perform new band-structure and state-density calculations, and then repeat SCFC with the new state densities. 

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