Co-reporter:Timothy C. King;Peter D. Matthews;Hugh Glass;Jonathan A. Cormack;Dr. Juan Pedro Holgado;Dr. Michal Leskes;Dr. John M. Griffin;Dr. Oren A. Scherman;Dr. Paul D. Barker; Clare P. Grey;Dr. Siân E. Dutton; Richard M. Lambert;Dr. Gary Tustin; Ali Alavi; Dominic S. Wright
Angewandte Chemie 2015 Volume 127( Issue 20) pp:6017-6021
Publication Date(Web):
DOI:10.1002/ange.201412200
Abstract
Previous theoretical studies of C3B have suggested that boron-doped graphite is a promising H2- and Li-storage material, with large maximum capacities. These characteristics could lead to exciting applications as a lightweight H2-storage material for automotive engines and as an anode in a new generation of batteries. However, for these applications to be realized a synthetic route to bulk C3B must be developed. Here we show the thermolysis of a single-source precursor (1,3-(BBr2)2C6H4) to produce graphitic C3B, thus allowing the characteristics of this elusive material to be tested for the first time. C3B was found to be compositionally uniform but turbostratically disordered. Contrary to theoretical expectations, the H2- and Li-storage capacities are lower than anticipated, results that can partially be explained by the disordered nature of the material. This work suggests that to model the properties of graphitic materials more realistically, the possibility of disorder must be considered.
Co-reporter:Timothy C. King;Peter D. Matthews;Hugh Glass;Jonathan A. Cormack;Dr. Juan Pedro Holgado;Dr. Michal Leskes;Dr. John M. Griffin;Dr. Oren A. Scherman;Dr. Paul D. Barker; Clare P. Grey;Dr. Siân E. Dutton; Richard M. Lambert;Dr. Gary Tustin; Ali Alavi; Dominic S. Wright
Angewandte Chemie International Edition 2015 Volume 54( Issue 20) pp:5919-5923
Publication Date(Web):
DOI:10.1002/anie.201412200
Abstract
Previous theoretical studies of C3B have suggested that boron-doped graphite is a promising H2- and Li-storage material, with large maximum capacities. These characteristics could lead to exciting applications as a lightweight H2-storage material for automotive engines and as an anode in a new generation of batteries. However, for these applications to be realized a synthetic route to bulk C3B must be developed. Here we show the thermolysis of a single-source precursor (1,3-(BBr2)2C6H4) to produce graphitic C3B, thus allowing the characteristics of this elusive material to be tested for the first time. C3B was found to be compositionally uniform but turbostratically disordered. Contrary to theoretical expectations, the H2- and Li-storage capacities are lower than anticipated, results that can partially be explained by the disordered nature of the material. This work suggests that to model the properties of graphitic materials more realistically, the possibility of disorder must be considered.
Co-reporter:Robert E. Thomas, Catherine Overy, George H. Booth, and Ali Alavi
Journal of Chemical Theory and Computation 2014 Volume 10(Issue 5) pp:1915-1922
Publication Date(Web):March 19, 2014
DOI:10.1021/ct400835u
The initiator full configuration interaction quantum Monte Carlo method (i-FCIQMC) is applied to the binding curve of N2 in Slater-determinant Hilbert spaces formed of both canonical restricted Hartree–Fock (RHF) and symmetry-broken unrestricted Hartree–Fock (UHF) orbitals. By explicit calculation, we demonstrate that the technique yields the same total energy for both types of orbital but that as the bond is stretched, FCI expansions expressed in unrestricted orbitals are substantially more compact than their restricted counterparts and more compact than those expressed in split-localized orbitals. These unrestricted Hilbert spaces, however, become nonergodic toward the dissociation limit, and the total wave function may be thought of as the sum of two weakly coupled, spin-impure, functions whose energies are nonetheless very close to the exact energy. In this limit, it is a challenge for i-FCIQMC to resolve a spin-pure wave function. The use of unrestricted natural orbitals is a promising remedy for this problem, as their expansions are more strongly weighted toward lower excitations of the reference, and they provide stronger coupling to higher excitations than do UHF orbitals.
Co-reporter:Deidre Cleland, George H. Booth, Catherine Overy, and Ali Alavi
Journal of Chemical Theory and Computation 2012 Volume 8(Issue 11) pp:4138-4152
Publication Date(Web):September 13, 2012
DOI:10.1021/ct300504f
The initiator full configuration interaction quantum Monte Carlo (i-FCIQMC) method has recently been developed as a highly accurate stochastic electronic structure technique. It has been shown to calculate the exact basis-set ground state energy of small molecules, to within modest stochastic error bars, using tractable computational cost. Here, we use this technique to elucidate an often troublesome series of first-row diatomics consisting of Be2, C2, CN, CO, N2, NO, O2, and F2. Using i-FCIQMC, the dissociation energies of these molecules are obtained almost entirely to within chemical accuracy of experimental results. Furthermore, the i-FCIQMC calculations are performed in a relatively black-box manner, without any a priori knowledge or specification of the wave function. The size consistency of i-FCIQMC is also demonstrated with regards to these diatomics at their more multiconfigurational stretched geometries. The clear and simple i-FCIQMC wave functions obtained for these systems are then compared and investigated to demonstrate the dynamic identification of the dominant determinants contributing to significant static correlation. The appearance and nature of such determinants is shown to provide insight into both the i-FCIQMC algorithm and the diatomics themselves.
Co-reporter:Matthew Dyer;Changjun Zhang Dr. Dr.
ChemPhysChem 2005 Volume 6(Issue 9) pp:
Publication Date(Web):11 JUL 2005
DOI:10.1002/cphc.200400638
Quantum diffusion constants of H and its isotopes in Pd and Nb are computed using Kubo theory applied on potential-energy surfaces obtained from density functional theory. The figure shows an excited state of H in Pd. This state is among several states which are below the classical barrier but are also delocalised between the octahedral and tetrahedral sites that contribute to quantum diffusion at low temperatures.
