$\alpha$-T boron crystals reported in the last century are now believed to contain C or N impurities and the crystals reported by Hoard [@Hoard58] may belong to this class, too. Hereafter we will call these crystals [*traditional*]{} $\alpha$-T boron. Such traditional $\alpha$-T boron always contains impurities such as C or N, and exhibits a deviation from stoichiometry.

     Author       Hoard [@Hoard58]                                Hyodo [@HyodoTh]   Ekimov [@Ekimov11]       Qin [@Qin12]   Kurakevych [@Kurakevych12] 
  ------------- ------------------ ----------------------- ----------------------- -------------------- ------------------ ---------------------------- --------------------
     Formula        ${\rm B_{50}}$   ${\rm B_{50}C_{1.9}}$   ${\rm B_{50}N_{1.8}}$     ${\rm B_{52.2}}$   ${\rm B_{51.5}}$               ${\rm B_{50}}$      various C conc.
                                                                                                                                                                including 0%
   $a_{0}$ (Å)               8.750                   8.753                   8.634                8.808             9.0508                         8.71   $ 8.775 \sim 8.93$
                                 0                 $+0.03$                  $-1.3$              $+0.63$             $+2.8$                      $-0.46$    $+0.28 \sim +2.1$
   $c_{0}$ (Å)               5.060                   5.093                   5.128                5.047             5.1341                         5.00    $5.064 \sim 5.08$
                                 0                 $+0.65$                  $+1.3$              $-0.27$             $+1.5$                      $-0.01$   $+0.08 \sim +0.40$
      Site                                                                                                                                              
      $2a$                       -                    12.8                     1.4                   11                  -                              
      $2b$                     100               \(C) 90.8               \(N) 92.9                   93                100                              
      $4c$                       -                       -                       -                    0                 31                              
      $4g$                       -                       -                       -                    -                  6                              
      $4d$                       -                       -                       -                    0                  -                              
      $8h$                       -                    11.2                     2.6                    2                  -                              
      $8i$                       -                     9.8                      23                   24                  -                              

  : A comparison of different $\alpha$-tetragonal boron structures that were reported in the literature. The lattice parameters and occupancies of 