Partition density functional theory

Partition density functional theory (PDFT) is a method for dividing a molecular electronic structure calculation into fragment calculations. The molecular density and energy corresponding to Kohn Sham density-functional theory (KS-DFT) may be exactly recovered from these fragments. Each fragment acts as an isolated system except for the influence of a global one-body \u27partition\u27 potential which deforms the fragment densities. In this work, the developments of PDFT are put into the context of other fragment-based density functional methods. We developed three numerical implementations of PDFT: One within the NWChem computational chemistry package using basis sets, and the other two developed from scratch using real-space grids. It is shown that all three of these programs can exactly reproduce a KS-DFT calculation via fragment calculations. The first of our in-house codes handles non-interacting electrons in arbitrary one-dimensional potentials with any number of fragments. This code is used to explore how the exact partition potential changes for different partitionings of the same system and also to study features which determine which systems yield non-integer PDFT occupations and which systems are locked into integer PDFT occupations. The second in-house code, CADMium, performs real-space calculations of diatomic molecules. Features of the exact partition potential are studied for a variety of cases and an analytical formula determining singularities in the partition potential is derived. We introduce an approximation for the non-additive kinetic energy and show how this quantity can be computed exactly. Finally a PDFT functional is developed to address the issues of static correlation and delocalization errors in approximations within DFT. The functional is applied to the dissociation of H2+ and H2

Oil Abundance and Violent Political Conflict: A Critical Assessment

This paper addresses one of the empirical claims of the 'resource curse' argument, namely that oil abundance raises the probability of political violence. I argue that the two main theoretical premises of the oil-civil-war link, rent-seeking and the rentier state model, fail to provide a convincing argument as to why oil economies are more vulnerable to the onset of civil war. I find that three often-mentioned mechanisms as to why oil economies succumb to political violence not convincing; that oil economies are poor economic performers; that oil economies generate high corruption; and that oil economies tend to produce authoritarian regimes. I also examine the empirical evidence on the oil-civil-war link and conclude that the results are not robust. I conclude with some policy implications.