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BETA
Latham, Christopher D.ORCID iD iconorcid.org/0000-0003-0509-925x
Alternative names
Publications (10 of 17) Show all publications
Adjizian, J., Latham, C., Öberg, S., Briddon, P. & Heggie, M. (2013). DFT study of the chemistry of sulfur in graphite, including interactions with defects, edges and folds (ed.). Paper presented at . Carbon, 62, 256-262
Open this publication in new window or tab >>DFT study of the chemistry of sulfur in graphite, including interactions with defects, edges and folds
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2013 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 62, p. 256-262Article in journal (Refereed) Published
Abstract [en]

Sulfur has several roles, desirable and undesirable, in graphitization. We perform density functional theory calculations within the local density approximation to define the structures and energetics of sulphur in graphite, including its interactions with point defects and edges, in order to understand its role in the later stages of graphitization. We find sulphur does not cross-link layers, except where there are defects. It reacts very strongly with vacancies in neighbouring layers to form a six coordinate split vacancy structure, analogous to that found in diamond. It is also highly stable at basal edge sites, where, as might be expected, the size and valency of sulfur can be easily accommodated. This suggests a role for sulphur in stabilizing graphene edges, and following from this, we show that sulfur dimers can open, i.e. unzip, folds in graphite rapidly and exothermically.

National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-15530 (URN)10.1016/j.carbon.2013.05.063 (DOI)000322931300028 ()2-s2.0-84880272854 (Scopus ID)f0fbdee5-8cdc-4de6-9445-9b157a3ae748 (Local ID)f0fbdee5-8cdc-4de6-9445-9b157a3ae748 (Archive number)f0fbdee5-8cdc-4de6-9445-9b157a3ae748 (OAI)
Note
Validerad; 2013; 20130617 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Trevethan, T., Dyulgerova, P., Latham, C., Heggie, M., Seabourne, C., Scott, A., . . . Rayson, M. (2013). Extended interplanar linking in graphite formed from vacancy aggregates (ed.). Paper presented at . Physical Review Letters, 111(9), Article ID 95501.
Open this publication in new window or tab >>Extended interplanar linking in graphite formed from vacancy aggregates
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2013 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 111, no 9, article id 95501Article in journal (Refereed) Published
Abstract [en]

The mechanical and electrical properties of graphite and related materials such as multilayer graphene depend strongly on the presence of defects in the lattice structure, particularly those which create links between adjacent planes. We present findings which suggest the existence of a new type of defect in the graphite or graphene structure which connects adjacent planes through continuous hexagonal sp² bonding alone and can form through the aggregation of individual vacancy defects. The energetics and kinetics of the formation of this type of defect are investigated with atomistic density functional theory calculations. The resultant structures are then employed to simulate high resolution transmission electron microscopy images, which are compared to recent experimental images of electron irradiation damaged graphite.

National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-4875 (URN)10.1103/PhysRevLett.111.095501 (DOI)000323610800018 ()2-s2.0-84884248341 (Scopus ID)2e04b38b-a977-47ca-89ca-76cadc5ed5a3 (Local ID)2e04b38b-a977-47ca-89ca-76cadc5ed5a3 (Archive number)2e04b38b-a977-47ca-89ca-76cadc5ed5a3 (OAI)
Note
Validerad; 2013; 20130904 (latham)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Latham, C. D., Heggie, M. I., Alatalo, M., Öberg, S. & Briddon, P. R. (2013). The contribution made by lattice vacancies to the Wigner effect in radiation-damaged graphite (ed.). Paper presented at . Journal of Physics: Condensed Matter, 25(13), Article ID 135403.
Open this publication in new window or tab >>The contribution made by lattice vacancies to the Wigner effect in radiation-damaged graphite
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2013 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 13, article id 135403Article in journal (Refereed) Published
Abstract [en]

Models for radiation damage in graphite are reviewed and compared, leading to a re-examination of the contribution made by vacancies to annealing processes. A method based on density functional theory, using large supercells with orthorhombic and hexagonal symmetry, is employed to calculate properties and behaviour of lattice vacancies and displacement defects. It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K. Migration of isolated monovacancies is estimated to have an activation energy Ea ≈ 1.1 eV. Coalescence into divacancy defects occurs in several stages, with different barriers at each stage, depending on the path. The formation of pairs ultimately yields up to 8.9 eV energy, which is nearly 1.0 eV more than the formation energy for an isolated monovacancy. Processes resulting in vacancy coalescence and annihilation appear to be responsible for the main Wigner energy release peak in radiation-damaged graphite, occurring at about 475 K.

National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-16152 (URN)10.1088/0953-8984/25/13/135403 (DOI)000315992900010 ()2-s2.0-84875208474 (Scopus ID)fbf0395a-7baf-49ee-8919-2ec96908a566 (Local ID)fbf0395a-7baf-49ee-8919-2ec96908a566 (Archive number)fbf0395a-7baf-49ee-8919-2ec96908a566 (OAI)
Note
Validerad; 2013; Bibliografisk uppgift: Article no 135403; 20130305 (latham)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Berezovsky, V., Men'shikov, L., Öberg, S. & Latham, C. (2008). Effect of dipole-dipole interactions between atoms in an active medium (ed.). Paper presented at . Journal of the Optical Society of America. B, Optical physics, 25(3), 458-462
Open this publication in new window or tab >>Effect of dipole-dipole interactions between atoms in an active medium
2008 (English)In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 25, no 3, p. 458-462Article in journal (Refereed) Published
Abstract [en]

On the basis of the results of numerical modeling, it is shown that dipole-dipole interactions among atoms in the active medium strongly influences the character of the associated superradiation. The main effect is to make the nuclear subsystem behave chaotically. Its strength increases with the atom density and leads to the suppression of distant collective correlations and superradiation. Near correlations between the atoms are established, causing a confinement effect: a shielding of radiation in the active medium.

National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-4404 (URN)10.1364/JOSAB.25.000458 (DOI)000254545700022 ()2-s2.0-44349163955 (Scopus ID)259ea430-0a2e-11dd-ae49-000ea68e967b (Local ID)259ea430-0a2e-11dd-ae49-000ea68e967b (Archive number)259ea430-0a2e-11dd-ae49-000ea68e967b (OAI)
Note
Validerad; 2008; 20080414 (pafi)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Berezovsky, V., Men'shikov, L., Öberg, S. & Latham, C. (2008). Effect of the dipole-dipole interaction of particles in an active medium on the character of superradiation (ed.). Paper presented at . Plasma physics reports (Print), 34(7), 555-561
Open this publication in new window or tab >>Effect of the dipole-dipole interaction of particles in an active medium on the character of superradiation
2008 (English)In: Plasma physics reports (Print), ISSN 1063-780X, E-ISSN 1562-6938, Vol. 34, no 7, p. 555-561Article in journal (Refereed) Published
Abstract [en]

The motion of a system of interacting nonlinear charged oscillators is investigated numerically. Because of nonlinearity, the total collective electric field gives rise to a phasing effect-correlations in the phases of the oscillators. The consequence is superradiation-the enhanced spontaneous short-term emission of the energy stored in the oscillators. It is shown that the oscillations of the oscillators become stochastic because of the dipole-dipole interaction between them and their nearest neighbors. As a result, as the density of the oscillators increases, distant collective correlations are suppressed, superradiation ceases to be generated, and radiation is shielded in the medium. The phenomena considered in the present paper can play an important role in cyclotron emission from a plasma and thus should be taken into account in emission calculations. The process whereby the energy of the transverse electron motion in electron cooling devices decreases is analyzed as an example. This process occurs as a result of the development of cyclotron maser instability and has the nature of superradiation. The onset of correlations between individual electrons moving in their Larmor circles is the initial, linear stage of instability developing in the plasma. Superradiation is the final, nonlinear instability stage.

National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-15947 (URN)10.1134/S1063780X08070040 (DOI)000257780400004 ()2-s2.0-47849104195 (Scopus ID)f86666c0-7363-11dd-a60f-000ea68e967b (Local ID)f86666c0-7363-11dd-a60f-000ea68e967b (Archive number)f86666c0-7363-11dd-a60f-000ea68e967b (OAI)
Note
Validerad; 2008; 20080826 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Latham, C., Öberg, S., Briddon, P. & Louchet, F. (2006). A pseudopotential density functional theory study of native defects and boron impurities in FeAl (ed.). Paper presented at . Journal of Physics: Condensed Matter, 18(39), 8859-8876
Open this publication in new window or tab >>A pseudopotential density functional theory study of native defects and boron impurities in FeAl
2006 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 18, no 39, p. 8859-8876Article in journal (Refereed) Published
Abstract [en]

The structures and energies of point defects and point defect complexes in B 2 iron aluminium FeAl are calculated using a local density functional theory based method with large supercells. Particular emphasis is given to pseudopotential quality, choice of chemical potentials used to calculate defect formation energies, and how these are affected by magnetism. Both purely native defects and those containing boron atoms are considered. It is found that the relative stabilities of isolated point defects versus defect complexes depends on whether the material contains excess iron or aluminium. The situation in material containing boron is further complicated by the existence of iron borides in more than one form. We propose that the interaction between point defects, dislocations, and antiphase boundaries, where the local atomic environment has some similarities with antisite defects, also depends on the alloy composition. It is likely that these interactions are part of the underlying mechanism responsible for the unusual mechanical properties of iron aluminides.

Keywords
density functional theory, pseudopotentials, yield stress anomaly, intermetallics, FeAl, FeB, Fe2B, Natural sciences - Physics, Materials science - Functional materials, Naturvetenskap - Fysik, Teknisk materialvetenskap - Funktionella material
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-8284 (URN)10.1088/0953-8984/18/39/016 (DOI)000241269800019 ()2-s2.0-33748862049 (Scopus ID)6c64ef40-bb7a-11db-b560-000ea68e967b (Local ID)6c64ef40-bb7a-11db-b560-000ea68e967b (Archive number)6c64ef40-bb7a-11db-b560-000ea68e967b (OAI)
Note
Validerad; 2006; 20070213 (kani)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Latham, C., Ganchenkova, M., Nieminen, R., Nicolaysen, S., Alatalo, M., Öberg, S. & Briddon, P. (2006). Electronic structure calculations for substitutional copper and monovacancies in silicon (ed.). Paper presented at Nordic Semiconductor Meeting : 18/08/2005 - 19/08/2005. Physica Scripta, 2006(T126), 61-64
Open this publication in new window or tab >>Electronic structure calculations for substitutional copper and monovacancies in silicon
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2006 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 2006, no T126, p. 61-64Article in journal (Refereed) Published
Abstract [en]

Two different computer program packages based on the self-consistent local-spin-density approximation-aimpro and vasp-are employed in this study of substitutional copper CuSi and monovacancies VSi in silicon, including the effects of their charge state. The programs differ in the types of basis sets and pseudopotentials they use, each with their own relative merits, while being similar in overall quality. This approach aims to reduce uncertainty in the results, particularly for small or subtle effects, where the risk is greatest that the conclusions are affected by artifacts specific to a particular implementation. The electronic structures of the two defects are closely related, hence they are expected to behave in a similar manner. For both defects structural distortions resulting in lower point group symmetries than Td (the highest possible) are found. This is in good agreement with the results of previous studies of VSi. Much less is known about symmetry-lowering effects for CuSi; however, the electronic levels of CuSi have been measured accurately, while those for VSi are less accessible. Calculating them is a challenging task for theory. The strategy we adopt, based purely on comparing total energies of supercells in different charge states, with and without model defects, reproduces the three known levels for CuSi reasonably well. Satisfactory results are also obtained for VSi in so far as can be judged for this more complex case.

Keywords
density functional theory, doping, point defects, impurities, lattice vacancies, electronic band structure, electronic energy levels, Jahn-Teller effect, semiconductors, silicon, Si, copper, Cu, Natural sciences - Physics, Materials science - Functional materials, Naturvetenskap - Fysik, Teknisk materialvetenskap - Funktionella material
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-26833 (URN)10.1088/0031-8949/2006/T126/014 (DOI)000246789700015 ()2-s2.0-33750826129 (Scopus ID)0172f9e0-bb7d-11db-b560-000ea68e967b (Local ID)0172f9e0-bb7d-11db-b560-000ea68e967b (Archive number)0172f9e0-bb7d-11db-b560-000ea68e967b (OAI)
Conference
Nordic Semiconductor Meeting : 18/08/2005 - 19/08/2005
Note
Validerad; 2006; 20070213 (kani); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Latham, C., Alatalo, M., Nieminen, R., Jones, R., Öberg, S. & Briddon, P. (2005). Passivation of copper in silicon by hydrogen (ed.). Paper presented at . Physical Review B. Condensed Matter and Materials Physics, 72(23)
Open this publication in new window or tab >>Passivation of copper in silicon by hydrogen
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2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 23Article in journal (Refereed) Published
Abstract [en]

The structures and energies of model defects consisting of copper and hydrogen in silicon are calculated using the AIMPRO local-spin-density functional method. For isolated copper atoms, the lowest energy location is at the interstitial site with Td symmetry. Substitutional copper atoms are found to adopt a configuration with D2d symmetry. We conclude that the symmetry is lowered from Td due to the Jahn-Teller effect. Interstitial hydrogen atoms are found to bind strongly to substitutional copper atoms with an energy that is more than the difference in formation energy over the interstitial site for Cu. The resulting complex has C2v symmetry in the -2 charge state where the H atom is situated about 1.54 Å away from the Cu atom in a [100] direction. In other charge states the symmetry of the defect is lowered to Cs or C1. A second hydrogen atom can bind to this complex with nearly the same energy as the first. Two structures are found for copper dihydride complexes that have nearly equal energies; one with C2 symmetry, and the other with Cs symmetry. The binding energy for a third hydrogen atom is slightly more than for the first. Calculated electronic levels for the model defects relative to one another are found to be in fair to good agreement with experimental data, except for the copper-dihydride complex. The copper trihydride complex has no deep levels in the bandgap, according to our calculations.

Keywords
density functional theory, doping, point defects, impurities, lattice vacancies, electronic band structure, electronic energy levels, Jahn-Teller effect, semiconductors, silicon, Si, copper, Cu, hydrogen, Natural sciences - Physics, Materials science - Functional materials, Naturvetenskap - Fysik, Teknisk materialvetenskap - Funktionella material
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-7800 (URN)10.1103/PhysRevB.72.235205 (DOI)000234336000053 ()2-s2.0-29844434328 (Scopus ID)63889860-bcf4-11db-9be7-000ea68e967b (Local ID)63889860-bcf4-11db-9be7-000ea68e967b (Archive number)63889860-bcf4-11db-9be7-000ea68e967b (OAI)
Note
Validerad; 2005; Bibliografisk uppgift: Paper id:: 235205; 20070215 (kani)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Latham, C., Jones, R., Öberg, S., Nieminen, R. & Briddon, P. (2003). Calculated properties of nitrogen-vacancy complexes in beryllium- and magnesium-doped GaN (ed.). Paper presented at . Physical Review B. Condensed Matter and Materials Physics, 68(20), 205209
Open this publication in new window or tab >>Calculated properties of nitrogen-vacancy complexes in beryllium- and magnesium-doped GaN
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2003 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 20, p. 205209-Article in journal (Refereed) Published
Abstract [en]

The properties of defect complexes consisting of a nitrogen vacancy with a substitutional beryllium or magnesium atom on neighboring lattice sites in hexagonal GaN are calculated using the AIMPRO local-density-functional theory method. Both types of defects VN-BeGa and VN-MgGa are bound with respect to their isolated constituents. They do not appear to have any electronic levels in the bandgap, and are expected to be neutral defects. Important structural differences are found. In its minimum energy configuration, the Be atom in the VN-BeGa complex lies nearly in the same plane as the three equivalent N atoms nearest to it. Thus, it has shorter Be-N bonds than the Ga-N distance in the bulk crystal, while the Mg atom in the VN-MgGa complex occupies a position closer the lattice site of the Ga atom it replaces. Hence, the VN-BeGa complex has a larger open volume than the VN-MgGa complex. This is consistent with positron annihilation experiments [Saarinen et al., J. Cryst. Growth 246, 281 (2002); Hautakangas et al., Phys. Rev. Lett. 90, 137402 (2003)]. The frequency of the highest local vibrational mode of the VN-BeGa center is calculated to be within 3-4 % of an infrared absorption line detected in Be-doped GaN

Keywords
density functional theory, doping, positron annihilation, infrared spectroscopy, semiconductors, III-V, nitrides, GaN, Natural sciences - Physics, Materials science - Functional materials, Naturvetenskap - Fysik, Teknisk materialvetenskap - Funktionella material
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-12959 (URN)10.1103/PhysRevB.68.205209 (DOI)000187314400034 ()c1cb2c90-bdc0-11db-9be7-000ea68e967b (Local ID)c1cb2c90-bdc0-11db-9be7-000ea68e967b (Archive number)c1cb2c90-bdc0-11db-9be7-000ea68e967b (OAI)
Note
Validerad; 2003; 20070216 (kani)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Latham, C. D., Nieminen, R., Fall, C., Jones, R., Öberg, S. & Briddon, P. (2003). Calculated properties of point defects in Be-doped GaN (ed.). Paper presented at . Physical Review B. Condensed Matter and Materials Physics, 67(20), 205206
Open this publication in new window or tab >>Calculated properties of point defects in Be-doped GaN
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2003 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 20, p. 205206-Article in journal (Refereed) Published
Abstract [en]

The properties of several point defects in hexagonal gallium nitride that can compensate beryllium shallow acceptors (BeGa) are calculated using the AIMPRO method based on local density functional theory. BeGa itself is predicted to have local vibrational modes (LVM's) very similar to magnesium acceptors. The highest frequency is about 663 cm-1. Consistent with other recent studies, we find that interstitial beryllium double donors and single-donor beryllium split interstitial pairs at gallium sites are very likely causes of compensation. The calculations predict that the split interstitial pairs possess three main LVM's at about 1041, 789, and 738 cm-1. Of these, the highest is very close to the experimental observation in Be-doped GaN. Although an oxygen donor at the nearest-neighboring site to a beryllium acceptor (BeGa-ON) is also a prime suspect among defects that are possibly responsible for compensation, its highest frequency is calculated to be about 699 cm-1 and hence is not related in any way to the observed center. Another mode for this defect is estimated to be about 523 cm-1 and is localized on the ON atom. These two vibrations of BeGa-ON are thus equivalent to those for the isolated substitutional centers perturbed by the presence of their impurity partners.

Keywords
density functional theory, doping, point defects, positron annihilation, infrared spectroscopy, semiconductors, III-V, nitrides, GaN, Natural sciences - Physics, Materials science - Functional materials, Naturvetenskap - Fysik, Teknisk materialvetenskap - Funktionella material
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:ltu:diva-6938 (URN)10.1103/PhysRevB.67.205206 (DOI)000183483200033 ()544d0880-bffc-11db-834c-000ea68e967b (Local ID)544d0880-bffc-11db-834c-000ea68e967b (Archive number)544d0880-bffc-11db-834c-000ea68e967b (OAI)
Note
Validerad; 2003; 20070219 (kani)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0509-925x

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