Asymmetry and uncertainty in capital formation: An application to oil investment

,Oil; Investment

Elastic Oil. A primer on the economics of exploration and production

,Oil; Exploration: Production

Competing magnetic interactions in spin-1/2 square lattice: hidden order in Sr2_2VO4_4

With decreasing temperature Sr$_2$VO$_4$ undergoes two structural phase transitions, tetragonal-to-orthorhombic-to-tetragonal, without long-range magnetic order. Recent experiments suggest, that only at very low temperature Sr$_{2}$VO$_{4}$ might enter some, yet unknown, phase with long-range magnetic order, but without orthorhombic distortion. By combining relativistic density functional theory with an extended spin-1/2 compass-Heisenberg model we find an antiferromagnetic single-stripe ground state with highly competing exchange interactions, involving a non negligible inter-layer coupling, which places the system at the crossover between between the XY and Heisenberg picture. Most strikingly, we find a strong two-site "spin-compass" exchange anisotropy which is relieved by the orthorhombic distortion induced by the spin stripe order. Based on these results we discuss the origin of the hidden order phase and the possible formation of a spin-liquid at low temperatures

The electronic and magnetic structure of p-element (C,N) doped rutile-TiO2_{2}; A hybrid DFT study

We study the electronic and magnetic structure of carbon and nitrogen impurities and interstitials in rutile TiO${_2}$. To this end we perform \textit{ab-initio} calculations of a 48-atom supercell employing the VASP code. In order to obtain a realistic description of the electronic and magnetic structure, exchange and correlation are treated with the HSE06 hybrid functional. Both, atomic positions and cell dimensions are fully relaxed. Substitutional carbon and nitrogen are found to have a magnetic moment of 2 and 1$\mu{_B}$, respectively, with a tendency for anti-ferromagnetic long range order. For C/N on interstitial sites we find that carbon is non-magnetic while nitrogen always possesses a magnetic moment of 1$\mu{_B}$. We find that these interstitial positions are on a saddle point of the total energy. The stable configuration is reached when both carbon and nitrogen form a C-O and N-O dimer with a bond length close to the double bond for CO and NO. This result is in agreement with earlier experimental investigations detecting such N-O entities from XPS measurements. The frequencies of the symmetric stretching mode are calculated for these dimers, which could provide a means for experimental verification. For all configurations investigated both C and N states are found inside the TiO${_2}$ gap. These new electronic states are discussed with respect to tuning doped TiO${_2}$ for the application in photocatalysi

Ab-initio friction forces on the nanoscale: A DFT study of fcc Cu(111)

While there are a number of models that tackle the problem of calculating friction forces on the atomic level, providing a completely parameter-free approach remains a challenge. Here we present a quasi-static model to obtain an approximation to the nanofrictional response of dry, wearless systems based on quantum mechanical all-electron calculations. We propose a mechanism to allow dissipative sliding, which relies on atomic relaxations. We define two different ways of calculating the mean nanofriction force, both leading to an exponential friction-versus-load behavior for all sliding directions. Since our approach does not impose any limits on lengths and directions of the sliding paths, we investigate arbitrary sliding directions for an fcc Cu(111) interface and detect two periodic paths which form the upper and lower bound of nanofriction. For long aperiodic paths the friction force convergences to a value in between these limits. For low loads we retrieve the Derjaguin generalization of Amontons-Coulomb kinetic friction law which appears to be valid all the way down to the nanoscale. We observe a non-vanishing Derjaguin-offset even for atomically flat surfaces in dry contact.Comment: 9 pages, 8 figures, submitted to Physical Review

Valuation of International Oil Companies –The RoACE Era

High oil prices are normally expected to stimulate exploration and the development of new oil and gas fields. But over the last few years, financial analysts have focused strongly on short-term accounting return (RoACE) for benchmarking and valuation, and this has led to high capital discipline among oil and gas companies. We analyse how high oil prices can be explained in terms of an implicit capacity game between the oil companies, and explore the stability of the current equilibrium. Our approach is an investigation of a key assumption among financial analysts, namely the presumed positive relation between RoACE and stock market valuation. Based on panel data for 11 international oil and gas companies, we seek to establish econometric relations between market valuation on one hand, and simple financial and operational indicators on the other. Our findings do not support the perceived positive relation between reported RoACE and market-based multiples. Recent evidence also suggests that the stock market is increasingly concerned about reserve replacement and sustained profitable growth. The current high-price equilibrium is therefore hardly stable.