NQR, NMR, and X-ray crystal structure studies of [4-C2H5-C6H4NH3]2MBr4 (M=Zn, Cd)

2018 ◽  
Vol 73 (9) ◽  
pp. 611-616
Author(s):  
Hideta Ishihara ◽  
Hisashi Honda ◽  
Ingrid Svoboda ◽  
Hartmut Fuess
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Benzene Ring ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Unit Cell ◽  
Organic Layers ◽  
Nuclear Magnetic Resonance Spectra ◽  
Quadrupole Resonance

AbstractThe crystal structure of [4-C2H5-C6H4NH3]2ZnBr4 (1) has been determined at 150(2) K: triclinic, P1̅, a=724.82(2), b=1194.20(4), c=1322.26(4) pm, α=74.151(3), β=80.887(3), γ=80.434(3)°, and Z=2. There are two crystallographically independent cations in the unit cell of 1: one has its benzene ring perpendicular to the crystallographic a axis of the unit cell and the other one has its benzene ring perpendicular to the c axis. These cations are alternatingly located along the c axis and form organic layers, and the ZnBr4 anions form inorganic layers in between. Zn–Br···H–N hydrogen bonds are formed between cations and anions. In accordance with the crystal structure, four nuclear quadrupole resonance (NQR) lines of 81Br were observed. The temperature dependence of the 81Br NQR frequencies between 77 and 320 K shows a peculiar feature which is not due to a structural phase transition. The measurement of 13C nuclear magnetic resonance spectra at around T=340 K indicates a redistribution of cations. The temperature dependence of 81Br NQR frequencies and differential thermal analysis measurements show that [4-C2H5-C6H4NH3]2CdBr4 (2) undergoes a structural phase transition at around 190 K.

NQR and Crystal Structure of 4,5-Dichloroimidazole, C3H2N2Cl2

1992 ◽  
Vol 47 (1-2) ◽  
pp. 177-181 ◽  
Author(s):  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Unit Cell ◽  
Space Group ◽  
Temperature Range ◽  
Temperature Coefficients ◽  
Group D

AbstractThe two line 35Cl NQR spectrum of 4,5-dichloroimidazole was measured in the temperature range 77≦ T/K ≦ 389. The temperature dependence of the NQR frequencies conforms with the Bayer model and no phase transition is indicated in the curves v ( 35Cl)= f(T). Also the temperature coefficients of the 35Cl NQR frequencies are "normal". At 77 K the 35Cl NQR frequencies are 37.409 MHz and 36.172 MHz and at 389 K 35.758 MHz and 34.565 MHz. The compound crystallizes at room temperature with the tetragonal space group D44-P41212, Z = 8 molecules per unit cell; at 295 K : a = 684.2(5) pm, c = 2414.0(20) pm. The relations between the crystal structure and the NQR spectrum are discussed.

Phase transition in metal–organic complex trans-PtCl2(PEt3)2 under pressure: insights into the molecular and crystal structure

CrystEngComm ◽  
2018 ◽  
Vol 20 (26) ◽  
pp. 3728-3740 ◽  
Author(s):  
Naini Bajaj ◽  
Himal Bhatt ◽  
K. K. Pandey ◽  
H. K. Poswal ◽  
A. Arya ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bond ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Molecular And Crystal Structure ◽  
Supramolecular Architecture ◽  
Organic Complex ◽  
Metal Organic Complex ◽  
Metal Organic

Molecular reorientations result in structural phase transition in trans-PtCl2(PEt3)2 under pressure, leading to a hydrogen bond assisted supramolecular architecture.

A high temperature structural phase transition in crocoite (PbCrO4) at 1068 K: crystal structure refinement at 1073 K and thermal expansion tensor determination at 1000 K

2000 ◽  
Vol 64 (2) ◽  
pp. 291-300 ◽  
Author(s):  
K. S. Knight
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Thermal Expansion ◽  
High Temperature ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Structure Type ◽  
Temperature Phase ◽  
Thermal Expansion Tensor ◽  
Principal Axes

AbstractHigh-resolution, neutron time-of-flight, powder diffraction data have been collected on natural crocoite between 873 and 1073 K. Thermal analysis carried out in the 1920s had suggested that chemically pure PbCrO4 exhibited two structural phase transitions, at 964 K, to the β phase, and at 1056 K, to the γ phase. In this study, no evidence was found for the α-β structural phase transition, however a high-temperature phase transition was found at ∼1068 K from the ambient-temperature monazite structure type to the baryte structure type. The phase transition, close to the temperatures reported for the β to γ phase modifications, is first order and is accompanied by a change in volume of −1.6%. The crystal structure of this phase has been refined using the Rietveld method to agreement factors of Rp = 0.018, Rwp = 0.019, Rp = 0.011. No evidence for premonitory behaviour was found in the temperature dependence of the monoclinic lattice constants rom 873 K to 1063 K and these have been used to determine the thermal expansion tensor of crocoite just below the phase transition. At 1000 K the magnitudes of the tensor coefficients are α11, 2.66(1) × 10−5 K−1; α22, 2.04(1) × 10−5 K−1; α33, 4.67(4) × 10−5 K−1; and α13, −1.80(2) × 10−5 K−1 using the IRE convention for the orientation of the tensor basis. The orientation of the principal axes of the thermal expansion tensor are very close to those reported previously for the temperature range 50–300 K.

scholarly journals Structural Phase Transition and Related Thermoelectric Properties in Sn Doped AgBiSe2

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1016
Author(s):  
Xiao-Cun Liu ◽  
Ming-Yan Pan
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Thermoelectric Material ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Complex Structural

AgBiSe2, which exhibits complex structural phase transition behavior, has recently been considered as a potential thermoelectric material due to its intrinsically low thermal conductivity. In this work, we investigate the crystal structure of Sn-doped AgBiSe2 through powder X-ray diffraction and differential scanning calorimetry measurements. A stable cubic Ag1−x/2Bi1−x/2SnxSe2 phase can be obtained at room temperature when the value of x is larger than 0.2. In addition, the thermoelectric properties of Ag1−x/2Bi1−x/2SnxSe2 (x = 0.2, 0.25, 0.3, 0.35) are investigated, revealing that Ag1−x/2Bi1−x/2SnxSe2 compounds are intrinsic semiconductors with a low lattice thermal conductivity. This work provides new insights into the crystal structure adjustment of AgBiSe2 and shows that Ag1−x/2Bi1−x/2SnxSe2 is a potentially lead-free thermoelectric material candidate.

Pressure-induced structural phase transition in Li4Ge

CrystEngComm ◽  
2018 ◽  
Vol 20 (39) ◽  
pp. 5949-5954 ◽  
Author(s):  
Chun-Mei Hao ◽  
Yunguo Li ◽  
Qiang Zhu ◽  
Xin-Yi Chen ◽  
Zhan-Xin Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Electronic Properties ◽  
Structural Phase Transition ◽  
First Principles ◽  
Structure Prediction ◽  
Structural Phase ◽  
Crystal Structure Prediction ◽  
First Principles Calculations ◽  
Structural Dynamic

The structural, dynamic, elastic, and electronic properties of Li4Ge were investigated by means of evolutionary crystal structure prediction in conjunction with first-principles calculations.

The Crystal Structure of [Mg2(H2O)6(HCO3)3]+Cl–, Containing a Magnesium-based Hetero-polycation

2008 ◽  
Vol 63 (12) ◽  
pp. 1347-1351 ◽  
Author(s):  
Robert E. Dinnebier ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Resolution ◽  
Structural Phase Transition ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structural Phase ◽  
Close Packing ◽  
Powder Diffraction Data ◽  
Hydrogen Carbonate

The crystal structure of di-magnesium hexahydrate trihydrogencarbonate chloride, [Mg2(H2O)6- (HCO3)3]+Cl−, has been determined from high-resolution laboratory powder diffraction data (lattice parameters at r. t.: a = 8.22215(2), c = 39.5044(2) Å, V = 2312.85(2) Å3, space group R3̄̄c, Z = 6). The crystal structure of [Mg2(H2O)6(HCO3)3]+Cl− is built up of alternating sheets of Cl− anions and complex [Mg2(H2O)6(HCO3)3]+ cations consisting of two Mg(OH2)3O3 octahedra interconnected by three disordered hydrogen carbonate groups. The packing can be described as a cubic close packing of [Mg2(H2O)6(HCO3)3]+ cations with the Cl− anions filling all octahedral voids. In the temperature range from r. t. up to decomposition, which takes place in the range 398 K < T < 413 K, no structural phase transition occurs.

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