Classical turning surfaces of Kohn–Sham potentials separate classically allowed regions(CARs)from classically forbidden regions(CFRs).They are useful for understanding many chemical properties of molecules but need n...Classical turning surfaces of Kohn–Sham potentials separate classically allowed regions(CARs)from classically forbidden regions(CFRs).They are useful for understanding many chemical properties of molecules but need not exist in solids,where the density never decays to zero.At equilibrium geometries,we find that CFRs are absent in perfect metals,rare in covalent semiconductors at equilibrium,but common in ionic and molecular crystals.In all materials,CFRs appear or grow as the internuclear distances are uniformly expanded.They can also appear at a monovacancy in a metal.Calculations with several approximate density functionals and codes confirm these behaviors.A classical picture of conduction suggests that CARs should be connected in metals,and disconnected in wide-gap insulators,and is confirmed in the limits of extreme compression and expansion.Surprisingly,many semiconductors have no CFR at equilibrium,a key finding for density functional construction.Nonetheless,a strong correlation with insulating behavior can still be inferred.Moreover,equilibrium bond lengths for all cases can be estimated from the bond type and the sum of the classical turning radii of the free atoms or ions.展开更多
基金A.D.K.acknowledges the support of the Department of Energy(DOE),Basic Energy Sciences under grant No.DE-SC0012575support from Temple University.S.J.C.acknowledges Engineering and Physical Sciences Research Council support on grant EP/P022782/1+1 种基金K.B.was supported by DOE under grant no.DE-FG02-08ER46496J.P.P.acknowledges the support of the National Science Foundation under grant number DMR-1939528.
文摘Classical turning surfaces of Kohn–Sham potentials separate classically allowed regions(CARs)from classically forbidden regions(CFRs).They are useful for understanding many chemical properties of molecules but need not exist in solids,where the density never decays to zero.At equilibrium geometries,we find that CFRs are absent in perfect metals,rare in covalent semiconductors at equilibrium,but common in ionic and molecular crystals.In all materials,CFRs appear or grow as the internuclear distances are uniformly expanded.They can also appear at a monovacancy in a metal.Calculations with several approximate density functionals and codes confirm these behaviors.A classical picture of conduction suggests that CARs should be connected in metals,and disconnected in wide-gap insulators,and is confirmed in the limits of extreme compression and expansion.Surprisingly,many semiconductors have no CFR at equilibrium,a key finding for density functional construction.Nonetheless,a strong correlation with insulating behavior can still be inferred.Moreover,equilibrium bond lengths for all cases can be estimated from the bond type and the sum of the classical turning radii of the free atoms or ions.
