Table 11. Scaled Point-Charge Approximation (sPCA) (See Eq 35) of Inter-Atomic Bielectronic Integrals for Nearest-Neighbor Interactions^a.

System	RAB	QA	QB	δAB	EclAB	scl	ExAB	sx
β-N2	1.108	0.003	0.003	2.999	0.220	b	–0.903	0.630
CO2	1.149	2.280	–1.140	1.323	–1.415	1.182	–0.426	0.699
Graphite	1.422	0.000	–0.001	1.202	0.037	b	–0.372	0.832
BN (hex.)	1.446	2.214	–2.213	0.452	–1.762	0.982	–0.135	0.816
Diamond	1.545	0.001	0.001	0.914	0.014	b	–0.284	0.907
BN (cubic)	1.561	2.160	–2.160	0.357	–1.587	1.004	–0.106	0.881
MgB2	1.782	–0.813	–0.813	0.983	0.166	0.845	–0.249	0.852
MgO	2.106	1.711	–1.712	0.129	–0.725	0.984	–0.029	0.884
LiCl	2.566	0.897	–0.899	0.044	–0.165	0.991	–0.007	0.819
Al	2.863	0.000	0.000	0.273	0.0013	b	–0.054	1.071
NaCl	2.896	0.875	–0.878	0.064	–0.1376	0.980	–0.010	0.866
CsCl	3.540	0.826	–0.827	0.126	–0.1019	0.996	–0.017	0.915
Na	3.667	0.000	0.000	0.108	0.0008	b	–0.013	0.836

^aEnergies in Ha, distances in Å, and charges in e units.

^bFor interactions between (nearly) noncharged atomic species, the scaling parameters s_cl become quite large, because the electrostatic interaction is then no longer dominated by a monopolar term. Nevertheless, the absolute error of this assumption is typically small, because the interactions are weak.