Interstitial dinitrogen makes<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>PtN</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>an insulating hard solid

Young, Andrea; Montoya, Javier A.; Sanloup, C.; Lazzeri, Michele; Gregoryanz, Eugene; Scandolo, Sandro

doi:10.1103/physrevb.73.153102

Cited by 131 publications

(106 citation statements)

References 24 publications

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“…Except for B2CN, they have been experimentally reported as superhard materials. The hardness of diamond-like cBC 2 N and cBC 5 even reach 76 (62) and 71 GPa, respectively, which are higher than that of cBN. Very recently, a new family of materials formed by heavy transition metals and light elements are proposed to be potential superhard since heavy transition metals can basically introduce high valence electron density into the compounds to resist both elastic and plastic deformation.…”

Section: Introductionmentioning

confidence: 91%

“…However, the true crystal structure of cBC 2 N still remains debatable. For the compounds formed by heavy transition metals and light elements, a variety of structure types within the substitutional methodology were considered to design new superhard materials, including the zinc-blende, rock salt, pyrite, rutile, fluorite, WC, CaCl 2 , MoC 2 , and CoSb 2 types [61][62][63][64][65][66][67][68][69][70][71][72]. The theoretical results demonstrated that these compounds possess ultrahigh bulk modulus (ultraincompressibility).…”

Section: Principles and Applicationsmentioning

confidence: 99%

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Predicting new superhard phases

Wang

2010

J. Superhard Mater.

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Section: Introductionmentioning

confidence: 91%

Section: Principles and Applicationsmentioning

confidence: 99%

Predicting new superhard phases

Wang

2010

J. Superhard Mater.

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“…DFT calculations had previously showed that PtN with the zinc blende structure as initially proposed became less stable at higher pressure due to having a lower density than the constituent elements at the same given pressure. A pyrite structure with covalently bonded N 2 units was then proposed ( Figure 5) [19,124,126]. Interestingly, this structure contains anionic N 2 units with bond lengths suggesting singly bonded species.…”

Section: New Nitrides Of the Pt Group Metalsmentioning

confidence: 99%

Nitrogen-rich transition metal nitrides

Salamat

Hector

Kroll

et al. 2013

Coordination Chemistry Reviews

131

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The solid state chemistry leading to the synthesis and characterization of metal nitrides with N:M ratios > 1 is summarized. Studies of these compounds represent an emerging area of research. Most transition metal nitrides have much lower nitrogen contents, and they often form with nonor sub-stoichiometric compositions. These materials are typically metallic with often superconducting properties, and they provide highly refractory, high hardness materials with many technological applications. The higher metal nitrides should achieve formal oxidation states (OS) attaining those found among corresponding oxides, and they are expected to have useful semiconducting properties. Only a very few examples of such high OS nitrogen-rich compounds are known at present. The main group elements typically form covalently bonded nitride ceramics such as Si 3 N 4 , Ge 3 N 4 and Sn 3 N 4 , and the early transition metals Zr and Hf produce Zr 3 N 4 and Hf 3 N 4 . However, the only main example of a highly nitrided transition metal compound known to date is Ta 3 N 5 , that has a formal oxidation state +5 and is a semiconductor with visible light absorption leading to applications as a pigment and in photocatalysis. New synthesis routes are being explored to study the possible formation of other N-rich materials that are predicted to exist by ab initio calculations. There is a useful interplay between theoretical predictions and experimental synthesis studies at ambient and high pressure conditions, as we explore and establish the existence and structure-property relations of these new nitride compounds and polymorphs. Here we review the state of current investigations and indicate possible new directions for further work.[a] European Synchrotron Radiation Facility,

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“…They can (5) 2 (P1) (6) 138 (P4 2 /ncm) (7) 205 (Pa3) (8) 224 (Pn3m) (9) [ be obtained by placing the PM atoms on an fcc lattice and the center of 111 -oriented nitrogen dimers on the octahedral interstitial sites of this lattice and allowing for atomic relaxations. For each nitrogen dimer there are four possible orientations, and thus for crystals with the periodicity of the fcc unit cell having four distinct PM-N 2 units, there are nine different crystal structures, two of which are the pyrite and marcasite phases.…”

mentioning

confidence: 99%

“…These include nitrides of Pt [2,3], Ir [3,4], Os [4] and Pd [5] Except for PdN 2 all these compounds have been shown to be at least metastable at ambient conditions. The resulting crystal structures have been investigated by several groups both experimentally and theoretically [2][3][4][5][6][7][8], and by now consensus has been reached concerning the observed crystal structures and stoichiometry (one metal atom for every nitrogen dimer). PtN 2 and PdN 2 are formed in the pyrite crystal structure, a cubic phase with the metal atoms occupying fcc sites.…”

mentioning

confidence: 99%

Thermodynamic Ground States of Platinum Metal Nitrides

et al. 2008

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The thermodynamic stabilities of various phases of the nitrides of the platinum metal elements are systematically studied using density functional theory. It is shown that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability with respect to those structures extends to 17 GPa for PtN2. Calculations show that the PtN2 simple tetragonal structures at this pressure are thermodynamically stable also with respect to phase separation. The fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures are further discussed. all these compounds have been shown to be at least metastable at ambient conditions. The resulting crystal structures have been investigated by several groups both experimentally and theoretically [2][3][4][5][6][7][8], and by now consensus has been reached concerning the observed crystal structures and stoichiometry (one metal atom for every nitrogen dimer). PtN 2 and PdN 2 are formed in the pyrite crystal structure, a cubic phase with the metal atoms occupying fcc sites. The nitrogen dimers are centered around the fcc octahedral interstitial sites, oriented in all the four possible 111 directions, such that all the nearest neighbor dimers make an angle of 70.53• with each other. A rotation of dimers such that two pairs point in the [111] and [111] direction, respectively, results in the marcasite structure, the predicted ground state phase of RuN 2 , RhN 2 and OsN 2 [7]. A small lattice distortion of marcasite then yields the monoclinic baddeleyite (CoSb 2 ) structure found in IrN 2 [5,7].The low-pressure phase diagrams of these systems are still not well understood. In particular their degree of thermodynamic stability has only been addressed briefly [3], where it was proposed that the Pt-N compound is only metastable at low pressures. In this work, we address this issue by calculating the formation enthalpies of all the PM nitrides as a function of pressure. We also report the discovery of two new low-energy crystal structures that at low pressures are thermodynamically more stable than any of the crystal phases that have up to now been synthesized experimentally or calculated from theory. To our knowledge, these new crystalline phases have not previously been observed in any other compound.

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Interstitial dinitrogen makesPtN2an insulating hard solid

Cited by 131 publications

References 24 publications

Predicting new superhard phases

Predicting new superhard phases

Nitrogen-rich transition metal nitrides

Thermodynamic Ground States of Platinum Metal Nitrides

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