What dictates alkane isomerization? A combined density functional theory and information-theoretic approach study

Alkanes are deceptively simple in their geometric structures, yet their electronic structures are a tough nut to crack. We employ two total energy partition schemes in density functional theory and the information-theoretic approach quantities to dissect the so-called isomerization problem. From our validation results, we have found theoretical methods, basis sets, dispersion corrections, and numerical integration grids all make contributions to the total energy difference. We highly recommend that PBE0-D3(BJ)/def2-QZVPP is a good choice for studying the longer alkane isomerization issue. We further find that the electrostatic potential dominates the isomerization of alkanes, provided that empirical dispersion is added. This conformational flexibility can be easily explained in the framework of conceptual density functional theory. This observation contrasts the commonly held belief that electron delocalization dictates alkane isomerization. We also find that molecular polarizability can be linearly correlated with some ITA quantities (such as Shannon entropy and Fisher information), indicating that simple density-based functions can be good descriptors of molecular properties.