Defect-induced strong localization of uranium dicarbide on the graphene surface.

Defects such as the most stable hexavacancy (V6) distribute widely on neutron-irradiated graphite surfaces, which play a dominant role in immobilizing radioactive products released from nuclear fuels. By performing DFT calculations, we explore the interaction of gaseous uranium dicarbide (UC2) molecules on a graphene nanosheet with a V6 defect, in order to investigate the behavior of the representative vapor species of uranium carbide fuels in reactor cores. Results suggest that UC2 can be trapped in the V6 defect with considerable binding energy of >10 eV, with all the six dangling bonds of the V6 defect being saturated by UC2. Bonding nature analyses also reveal that the U-C interaction lies in the synergistic interplay between electrostatic and covalent interaction with extensive participation of U valence electrons from 5f to 7p orbitals, which further stimulate polarization of semi-core 6p orbitals and their subsequent contributions to the bonding. This strong interaction leads to a favorable binding of UC2 to the defective graphite surface, which reduces the capability of nuclear graphite to retain harmful fission products by the vacancies being filled with UC2. These findings highlight substantial chemical reactivity and strong localization of UC2 on the widespread V6 defects in nuclear graphite, and may provide an important reference in establishing modern nuclear reactor safety at the atomic level.

[1]  M. Heggie,et al.  Vacancy diffusion and coalescence in graphene directed by defect strain fields. , 2014, Nanoscale.

[2]  Ruiqin Q. Zhang,et al.  Strong Adsorption Between Uranium Dicarbide and Graphene Surface Induced by f Electrons , 2013, 1310.4328.

[3]  M. Vijayakumar,et al.  Exploring the Interaction between Lithium ion and Defective Graphene Surface using Dispersion corrected DFT Studies , 2013 .

[4]  D. Morgan,et al.  DFT-based prediction of fission product sorption on carbon structures under O2 ingress conditions , 2013 .

[5]  Shubin Liu,et al.  Highly porous and stable metal–organic frameworks for uranium extraction , 2013 .

[6]  T. Hayton.  Recent developments in actinide-ligand multiple bonding. , 2013, Chemical communications.

[7]  Wei Zhang,et al.  Defect Induced Electronic Structure of Uranofullerene , 2013, Scientific Reports.

[8]  T. Ghanty,et al.  Prediction of a New Series of Thermodynamically Stable Actinide Encapsulated Fullerene Systems Fulfilling the 32-Electron Principle , 2012 .

[9]  Dongqi Wang,et al.  Theoretical study on the ground state structure of uranofullerene U@C82. , 2012, The journal of physical chemistry. A.

[10]  Dongqi Wang,et al.  Recent advances in computational actinoid chemistry. , 2012, Chemical Society reviews.

[11]  W. Schwarz,et al.  On the maximum bond multiplicity of carbon: unusual C≣U quadruple bonding in molecular CUO , 2012 .

[12]  D. Morgan,et al.  A review of fission product sorption in carbon structures , 2012 .

[13]  M. Otyepka,et al.  Interaction of Graphene and Arenes with Noble Metals , 2012 .

[14]  M. Katsnelson,et al.  Adsorption of cobalt on graphene: Electron correlation effects from a quantum chemical perspective , 2012, 1206.1222.

[15]  D. Morgan,et al.  First-principles study of Cs and Sr sorption on carbon structures , 2012 .

[16]  J. M. Kikkawa,et al.  Pentavalent uranium trans-dihalides and -pseudohalides. , 2012, Chemical communications.

[17]  M. F. Zalazar,et al.  On the molecular structure of uranium dicarbide: T-shape versus linear isomers. , 2012, The journal of physical chemistry. A.

[18]  Tian Lu,et al.  Multiwfn: A multifunctional wavefunction analyzer , 2012, J. Comput. Chem..

[19]  Z. Varga,et al.  Theoretical study of the structure and bonding in ThC2 and UC2. , 2012, The journal of physical chemistry. A.

[20]  J. Stanton,et al.  Reduced dimension discrete variable representation study of cis-trans isomerization in the S1 state of C2H2. , 2011, The Journal of chemical physics.

[21]  M. P. Kissane,et al.  A review of radionuclide behaviour in the primary system of a very-high-temperature reactor , 2009 .

[22]  D. Manara,et al.  Laser melting of uranium carbides , 2009 .

[23]  P. Pyykkö,et al.  A predicted organometallic series following a 32-electron principle: An@C28 (An = Th, Pa+, U2+, Pu4+). , 2009, Journal of the American Chemical Society.

[24]  G. Lombardo,et al.  Modeling vacancies and hydrogen impurities in graphene: A molecular point of view , 2008, 0808.0644.

[25]  G. Scuseria,et al.  Is fullerene C60 large enough to host a multiply bonded dimetal? , 2008, Journal of the American Chemical Society.

[26]  R. Telling,et al.  Radiation defects in graphite , 2007 .

[27]  R. Denning.  Electronic structure and bonding in actinyl ions and their analogs. , 2007, The journal of physical chemistry. A.

[28]  Sandra Schinzel,et al.  Structural and electronic analysis of lanthanide complexes: reactivity may not necessarily be independent of the identity of the lanthanide atom--a DFT study. , 2006, The journal of physical chemistry. A.

[29]  N. Kaltsoyannis.  Recent developments in computational actinide chemistry. , 2003, Chemical Society reviews.

[30]  Erik Van Lenthe,et al.  Optimized Slater‐type basis sets for the elements 1–118 , 2003, J. Comput. Chem..

[31]  M. Straka,et al.  Why are hexavalent uranium cyanides rare while U–F and U–O bonds are common and short? , 2003 .

[32]  David G. Martin,et al.  Considerations pertaining to the achievement of high burn-ups in HTR fuel , 2002 .

[33]  H. Stoll,et al.  Valence basis sets for relativistic energy-consistent small-core actinide pseudopotentials , 2001 .

[34]  Axel D. Becke,et al.  Chemical content of the kinetic energy density , 2000 .

[35]  Evert Jan Baerends,et al.  Geometry optimizations in the zero order regular approximation for relativistic effects. , 1999 .

[36]  Y. Kawazoe,et al.  Stable Vacancy Clusters in Neutron-Irradiated Graphite: Evidence for Aggregations with a Magic Number , 1999 .

[37]  Michael Dolg,et al.  Energy‐adjusted pseudopotentials for the actinides. Parameter sets and test calculations for thorium and thorium monoxide , 1994 .

[38]  C. S. Subbanna,et al.  R.f. spark source mass spectrometric studies of molecular ions , 1989 .

[39]  J. Perdew,et al.  Density-functional approximation for the correlation energy of the inhomogeneous electron gas. , 1986, Physical review. B, Condensed matter.

[40]  Frank Weinhold,et al.  Natural bond orbital analysis of near‐Hartree–Fock water dimer , 1983 .

[41]  S. Gupta,et al.  Observation and atomization energies of the gaseous uranium carbides, UC, UC2, UC3, UC4, UC5, and UC6 by high temperature mass spectrometry , 1979 .

[42]  Keiji Morokuma,et al.  Why do molecules interact? The origin of electron donor-acceptor complexes, hydrogen bonding and proton affinity , 1977 .

[43]  Keiji Morokuma,et al.  Molecular Orbital Studies of Hydrogen Bonds. III. C=O···H–O Hydrogen Bond in H2CO···H2O and H2CO···2H2O , 1971 .

[44]  J. Pople,et al.  Self‐Consistent Molecular‐Orbital Methods. IX. An Extended Gaussian‐Type Basis for Molecular‐Orbital Studies of Organic Molecules , 1971 .

[45]  Xin Wu,et al.  Dimetalloendofullerene U(2)@C(60) has a U-U multiple bond consisting of sixfold one-electron-two-center bonds. , 2007, Journal of the American Chemical Society.

[46]  B. Holian,et al.  The Interaction between Cesium and Graphite for Use in the Study of Surface Phenomena , 2005 .

[47]  Kenneth B. Wiberg,et al.  Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane , 1968 .