Unusual optical isotropy in anisotropic alkali metal perchlorates M<i>ClO</i><sub>4</sub>(M  =  Li, Na, K, Rb, Cs)

Jharapla, Prathap Kumar; Rao, E. Narsimha; Vaitheeswaran, G.

doi:10.1088/1361-648x/aae6fa

Cited by 5 publications

(9 citation statements)

References 59 publications

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“…Among the MTO 4 oxides, CdWO 4 and PbWO 4 are known as scintillator crystals, ZrGeO 4 and HfGeO 4 are used as phosphors, BaWO 4 , YVO 4 and GdTaO 4 are excellent laser-host materials, and CaMoO 4 and SrWO 4 are known for their use in batteries [13]. There are many other technological applications for these materials which span from nuclear waste storage to photocatalysis [14][15][16][17][18]. Interest in the characterization of MTO 4 oxides comes not only from their useful applications, but also from the diverse structural sequences they exhibit under high pressure [13,14].…”

Section: Introductionmentioning

confidence: 99%

Crystal structure and phase transition of TlReO₄: a combined experimental and theoretical study

Mondal¹,

Vaitheeswaran²,

Kennedy³

et al. 2020

J. Phys.: Condens. Matter

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The present work describes a density-functional theory (DFT) study of TlReO4 in combination with powder x-ray diffraction experiments as a function of temperature and Raman measurements at ambient temperature. X-ray diffraction measurements reveal three different structures as a function of temperature. A monoclinic structure (space group P21/c) is observed at room temperature while two isostructural tetragonal structures (space group I41/a) are found at low- and high-temperature. In order to complement the experimental results first-principles DFT calculations were performed to compute the structural energy differences. From the total energies it is evident that the monoclinic structure has the lowest total energy when compared to the orthorhombic structure, which was originally proposed to be the structure at room temperature, which agrees with our experiments. The structural and vibrational properties of the low- and room-temperature phase of TlReO4 have been calculated using DFT. Inclusion of van der Waals correction to the standard DFT exchange correlation functional is found to improve the agreement with the observed structural and vibrational properties. The Born effective charge of these phases has also been studied which shows a combination of ionic and covalent nature, resembling metavalent bonding. Calculations of zone-center phonon frequencies lead to the symmetry assignment of previously reported low-temperature Raman modes. We have determined the frequencies of the eight infrared-active, 13 Raman-active and three silent modes of low-temperature TlReO4 along with 105 infrared-active and 108 Raman-active modes for room-temperature TlReO4. Phonons of these two phases of TlReO4 are mainly divided into three regions which are below 150 cm−1 due to vibration of whole crystal, 250 to 400 cm−1 due to wagging, scissoring, rocking and twisting and above 900 cm−1 due to stretching in ReO4 tetrahedron. The strongest infrared peak is associated to the internal asymmetric stretching of ReO4 whereas the strongest Raman peak is associated to the internal symmetric stretching of ReO4. We have also measured the room-temperature Raman spectra of monoclinic TlReO4 identifying up to 28 modes. This Raman spectrum has been interpreted by comparison with the previously reported Raman frequencies of the low-temperature phase and our calculated Raman frequencies of low- and room-temperature phases of TlReO4.

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Section: Introductionmentioning

confidence: 99%

Crystal structure and phase transition of TlReO₄: a combined experimental and theoretical study

Mondal¹,

Vaitheeswaran²,

Kennedy³

et al. 2020

J. Phys.: Condens. Matter

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“…From the above discussion, we conclude that increase in atomic size changes the dispersive nature of alkali metal atoms series, the same was observed in our previous work based on alkali metal perchlorates. [ 35 ] Strong covalent nature between N and C (tetrazole ring) and ionic bonding between metal and surrounding N/C atoms has been observed.…”

Section: Resultsmentioning

confidence: 99%

“…[32] Our calcula- metal perchlorates. [35] Strong covalent nature between N and C (tetrazole ring) and ionic bonding between metal and surrounding N/C atoms has been observed.…”

Section: Born Effective Chargesmentioning

confidence: 99%

Comparative DFT study of vibrational, electronic, and optical properties of energetic alkali metal salts based on nitrogen‐rich 5‐aminotetrazole

2020

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This article presents a thorough density functional theory based comparative study on nitrogen-rich 5-aminotetrazole alkali metal salts M 5-At (M = Li, K, Rb, Cs). The calculated structural parameters using plane-wave pseudopotential method are consistent with the experimental results. The computed vibrational frequencies at ambient pressure show that vibrational modes in high energy region are due the N H bond of NH 2 group. Pressure variation IR spectra of these materials show clear frequency shifts where Li 5-At shows an overall red shift below 900 cm −1 contrary to the blue shift seen in other materials in this range. The born effective charge values reveal the presence of strong covalency between N, H, and C atoms whereas an increased ionic nature is seen as the atomic number of metal atoms increases. Furthermore, we used full potential linear augmented plane wave (FP-LAPW) method for calculating electronic structure and optical properties with TB-mBJ potential which provides an enhanced band gap for all materials compared to standard GGA functional. Electronic structure calculation reveals that all the compounds are indirect band gap insulators with the exception of Li 5-At. The computed partial density of states show mixed ionic-covalent nature in metal-N/C bonds and covalent nature in N C bonds. In addition, we are also presenting the optical properties such as real and imaginary dielectric constant, absorption, refraction, reflection, loss spectrum as functions of photon energy. From the optical properties we can conclude that all the studied compounds are optically anisotropic in nature and are good absorbers in the ultraviolet (UV) region. K E Y W O R D S 5-aminotetrazole, alkali metal salts, electronic properties, optical properties, vibrational properties 1 | INTRODUCTION Use of high nitrogen based energetic materials toward replacement of perchlorate in pyrotechnics is a subject of interest in recent times. Various derivative of perchlorate's are used since last few decades due to their intrinsic stability, low cost, reactivity, hygroscopic nature, and large positive oxygen balance. [1] Perchlorate based materials are now classified as environmentally dangerous and human health hazards. [2] These materials are believed to contaminate groundwater and interfere with the production and regulation of thyroid hormones, toxic and carcinogenic. [3,4] Research toward the replacement of rooted energetic materials (i.e., KClO 4 , NH 4 ClO 4 , Pb[N 3 ] 2) with increased performance and lower sensitivity to physical stimuli is hard to achieve. Over last few decades, rapid process in development of

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“…Sehingga ketika dilelehkan atau larut, maka akan mejadi sangat kondusif karena mobilisasi ion-ionnya. Menurut teori HSAB, senyawa dengan karakter ionic (111)(112)(113)(114)(115)(116) adalah yang terdiri dari asam kuat (85; 117; 118) dan basa kuat, ion kecil bermuatan sangat tinggi dengan perbedaan keelektronegatifan yang tinggi antara anion dan kation.…”

Section: Gerak Molekul Transfer Ionik Dalam Larutanunclassified

Vanadium Pentaoksida (V2O5) : Termodinamika Molecular dan Interaksi Ion dalam Larutan

Shafitri¹,

Zainul²

2019

Preprint

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Vanadium Pentaoksida merupakan senyawa dengan rumus V2O5. Vanadium Pentaoksida bewarna kuning orange dan ketika membeku membentuk kristal seperti jarum. Vanadium pentaoksda bersifat amfoter yang dapat bereaksi dengan asam maupun basa. Vanadium pentaoksida berfungsi atau dapat digunakan sebagai bahan katalis dari suatu larutan. Kelarutan senyawa ini terjadinya interaksi dari masing-masing molekul merupakan suatu proses dalam melakukan percobaan. V2O5 mengandung karbon pada batu bara, minyak mentah dan pasir tar. Tujuan dari review ini adalah uuntuk mengetahui tkarakteristik molecular secara termodinamika dan transfer ion dalam larutan. Metode yang digunakan adalah pemodelan komputasi di ChemOffice 15.0 yaitu Chem Draw Ultra 2D dan Chem Draw Bio 3D , dimana terlihat adanya pergerakan ion pada molekul. Data simulasi yang diperoleh dari referensi dalam pemodelan model vanadium pentaoksida, serta data dari hasil review beberapa jurnal penelitian yang berkaitan dengan senyawa vanadium pentaoksida. Hasil dari vanadium pentaoksida dilihat interaksinya dengan menetukan konduktifitas didapatkan 0,059 x 108 mho/cm, viskositas sebesar 0,579 mPa.s, daya hanyut sebesar 1,508 eV/cm, dan transfer ionic pada larutannya. Sifat termodinamikanya yaitu ∆So= 131 J/mol K, ∆foH= -1550,6 KJ/mol, ∆foG= -1419,5 KJ/mol,, Cp= 127,7 J/mol K. Senyawa ini dapat direaksikan dengan senyawa asam berlebih. Vanadium pentaoksida dapat bereaksi dalam air membentuk senyawa ion.

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Unusual optical isotropy in anisotropic alkali metal perchlorates MClO₄(M = Li, Na, K, Rb, Cs)

Cited by 5 publications

References 59 publications

Crystal structure and phase transition of TlReO₄: a combined experimental and theoretical study

Crystal structure and phase transition of TlReO₄: a combined experimental and theoretical study

Comparative DFT study of vibrational, electronic, and optical properties of energetic alkali metal salts based on nitrogen‐rich 5‐aminotetrazole

Vanadium Pentaoksida (V2O5) : Termodinamika Molecular dan Interaksi Ion dalam Larutan

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Unusual optical isotropy in anisotropic alkali metal perchlorates MClO4(M = Li, Na, K, Rb, Cs)

Cited by 5 publications

References 59 publications

Crystal structure and phase transition of TlReO4: a combined experimental and theoretical study

Crystal structure and phase transition of TlReO4: a combined experimental and theoretical study

Comparative DFT study of vibrational, electronic, and optical properties of energetic alkali metal salts based on nitrogen‐rich 5‐aminotetrazole

Vanadium Pentaoksida (V2O5) : Termodinamika Molecular dan Interaksi Ion dalam Larutan

Contact Info

Product

Resources

About

Unusual optical isotropy in anisotropic alkali metal perchlorates MClO₄(M = Li, Na, K, Rb, Cs)

Crystal structure and phase transition of TlReO₄: a combined experimental and theoretical study

Crystal structure and phase transition of TlReO₄: a combined experimental and theoretical study