order of the stability of these IS is $4c$ (-1.45), $8i$ (-1.35), and $8h$ (-1.28) (the values in parenthesis are differences in $\Delta E_{f}$ with respect to B$_{50}$). The $2b$ site is always a stable site, as seen from its perfect occupancy, i.e., removing a $2b$-site atom from B$_{50}$ requires an energy of +1.45 eV. The sites $2a$ (0.66) and $4g$ (0.98) are not stable.

  -------------- ----------------------------- ------ ------------ --------
   $N_{\rm at}$              Sites                      $\Delta V$ 
                                                          (eV/GPa) 
        49                   $-2b$               4.59       (4.76)    0.068
        50                                       3.14       (3.40)    0.052
        51                   $4c$                1.69       (1.66)    0.034
                             $8h$                1.72       (1.69)   -0.047
                             $8i$                1.80       (1.81)    0.035
                             $4g$                4.12       (4.13)    0.036
                             $2a$                3.80       (3.52)    0.049
        52        $2\times 4c$ (out-of-plane)     0.0        (0.0)      0.0
                    $2\times 4c$ (in-plane)      0.19       (0.15)   -0.006
                    $2\times 4c$ (nearest)       1.80       (1.82)   -0.006
                            $4c+8i$              0.19       (0.13)   -0.005
                            $4c+8h$              1.46       (1.49)    0.021
        53               $3\times 4c$            1.31       (1.11)   -0.028
                        $2\times 4c+8i$          2.68       (2.65)   -0.036
                       $2\times 4c+8i'$          2.67       (2.65)   -0.037
                        $2\times 4c+8h$          1.33       (1.10)   -0.024
        54               $4\times 4c$            2.40       (2.00)   -0.069
  -------------- ----------------------------- ------ ------------ --------

  : The formation energy $\Delta E_{f}$ of interstitial sites in $\alpha$-T boron within the primitive unit cell. The results indicate that B$_{52}$, with two 4c sites occupied, is the lowest-energy structure. The reference for $\Delta 