scholarly journals Structure and thermal properties associated with some hydrogen bonds in crystals, II. Thermal expansion

1939 ◽  
Vol 170 (941) ◽  
pp. 241-251 ◽  
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Zero Point ◽  
Lattice Vibrations ◽  
Point Energy ◽  
Binding Forces ◽  
Anisotropy Of Thermal Expansion ◽  
Made In

One of the most important thermodynamic properties of a crystal in relation to its structure is the thermal expansion, which provides information on the lattice vibrations, and thus indirectly on the binding forces. The experiments described in this paper were carried out with a view to obtaining fresh information on hydrogen and hydroxyl bonds in crystals from measurements of the thermal expansion. A comparison of the thermal expansion of corresponding- hydrogen and deuterium compounds from about 90° K to room temperature was made in order to distinguish between lattice deformations due to zero point energy and thermal energy respectively. The marked anisotropy of thermal expansion in crystals containing hydrogen bonds throws interesting light on the structure.

scholarly journals Structure and thermal properties associated with some hydrogen bonds in crystals I. The isotope effect

1939 ◽  
Vol 170 (941) ◽  
pp. 222-240 ◽  
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Hydrogen Bonds ◽  
Vibrational Spectrum ◽  
Isotope Effect ◽  
Vibrational Frequencies ◽  
Lattice Vibrations ◽  
X Ray

A study of the vibrational spectrum is one method of investigating the forces between atoms in a crystal. Since the lattice vibrations influence the distance between crystal planes, information on crystal forces can also be obtained from X-ray measurements of the thermal expansion. Finally, in crystals containing hydrogen it is possible by substituting deuterium to make large changes in certain vibrational frequencies, without altering any other factor which determines crystal structure.

Das Kombinationsschwingungsspektrum von Gips im Bereich von 10 000—1200 cm-1

1968 ◽  
Vol 23 (5) ◽  
pp. 708-715 ◽  
Author(s):  
V. Hohler ◽  
H. D. Lutz
Keyword(s):  
Hydrogen Bonds ◽  
Ir Spectrum ◽  
Room Temperature ◽  
Polarized Light ◽  
Water Molecules ◽  
Lattice Vibrations ◽  
Frequency Range ◽  
Sulfate Ions ◽  
Normal Vibrations

The IR-spectrum of gypsum (CaSO4·2 H2O) in the frequency range from 10 000 to 1200 cm-1 has been investigated with polarized light at room temperature. Between 3700 and 1200 cm-1, the measurements confirm the data of HASS and SUTHERLAND and as well as those of SCHAAK derived from IR and reflection measurements. The IR-spectrum shows a great number of bands, most of which can be assigned to combination and fundamental vibrations in terms of normal vibrations of the water molecules and the sulfate ions. The influence of the lattice vibrations is briefly discussed. The existence of hydrogen bonds between the water molecules and the sulfate ions gives rise to combinations of fundamental vibrations of both complexes.

Self-assembly of a Novel Three-dimensional Silver(I) Supramolecular Framework from Cationic Chains and Anionic Sheets

2010 ◽  
Vol 65 (2) ◽  
pp. 152-156
Author(s):  
Di Sun ◽  
Cheng-Feng Yang ◽  
Zhan-Hua Wei ◽  
Geng-Geng Luo ◽  
Na Zhang ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Hydrogen Bonds ◽  
Self Assembly ◽  
Room Temperature ◽  
Three Dimensional ◽  
Supramolecular Framework ◽  
Π Interactions ◽  
Π Stacking ◽  
Benzenedicarboxylic Acid

A new three-dimensional (3D) supramolecular framework, [Ag2(bipy)2(bdc)·4H2O]n 1, has been synthesized by the ultrasonic reaction of Ag2O, bipy and H2bdc (H2bdc = 1,4-benzenedicarboxylic acid; bipy = 4,4’-bipyridine) at room temperature. It exhibits a new 3D supramolecular framework which is built from cationic Ag-bipy chains and anionic bdc-H2O sheets through hydrogen bonds, π · · ·π stacking and C-H· · ·π interactions. Additionally, the photoluminescent and thermal properties of 1 were investigated.

Thermal Properties of Alkaline Earth Oxides II. Analysis of Experimental Results for MgO, CaO, SrO, and BaO

1970 ◽  
Vol 25 (6) ◽  
pp. 887-893 ◽  
Author(s):  
E. Gmelin
Keyword(s):  
Thermal Properties ◽  
Frequency Spectrum ◽  
Alkaline Earth ◽  
Characteristic Temperature ◽  
Low Frequency ◽  
Alkali Halides ◽  
Zero Point ◽  
Point Energy ◽  
Usual Procedure ◽  
Capacity Data

Abstract The heat capacities of MgO, CaO, SrO and BaO, reported in part I have been analysed in terms of the frequency spectrum of the lattice with the assumption that the effect of anharmonicity of the lattice may be neglected for T ≦ (ΘD/3). Following the usual procedure the n-th moments of the frequency spectrum with n = - 3, -2, - 1, 0, 1 to 6 were calculated from the experimental data. From the low frequency expansion the apparent Debye characteristic temperature at 0 °K, Θ0, is calculated to be in good agreement with Θ0 (elast.), calculated from elasticity data. Also the limiting values at high temperatures,Θ∞, and the zero point energy, Ez, have been calculated. A comparison between the heat capacity data, the elastic constants and thermal properties of these oxides and the alkali-halides suggest that the interatomic forces of the alkaline-earth-oxides are rather similar to those of the alkaline fluorides. But no specific divalent character has been detected for these oxides. An appreciable anharmonic effect is present for all oxides.

Comparison of Porous Ceramic Materials with Low Thermal Expansion Coefficient Prepared with SiC and Black-Al2O3

2008 ◽  
Vol 569 ◽  
pp. 321-324
Author(s):  
Isaías Juárez-Ramírez ◽  
Koji Matsumaru ◽  
Kozo Ishizaki ◽  
Leticia M. Torres-Martínez
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Raw Materials ◽  
Porous Ceramic ◽  
Ceramic Materials ◽  
X Ray Diffraction ◽  
Low Thermal Expansion ◽  
New Phase ◽  
Porous Ceramic Materials ◽  
Made In

Porous ceramic materials with low thermal expansion (LTE) at room temperature were prepared by heating a mixture of SiC or black-Al2O3, vitrified bonding material (VBM) and LiAlSiO4 at temperatures from 850°C to 1100°C. The mixture was prepared in adequate proportions to obtain a material with LTE according to previous works made in our laboratory. It was observed that a change in temperature provoked the formation of a new phase, LiAlSi3O8, which appears above 900°C. The presence of this new phase did not affect the thermal expansion value, keeping LTE at room temperature. All compounds showed around 40% of porosity, and Young’s modulus values of 30 GPa using black-Al2O3 or SiC. X-ray diffraction analysis (XRD) revealed that above 900°C the phase LiAlSi3O8 starts to appear as a consequence of the melting of VBM, which is reacting with the raw materials. SEM micrographs showed the presence of SiC or black-Al2O3 grains joined by VBM, which is acting as a bridge between them.

Synthesis and Detection the Thermal Expansion of CdSe Quantum Dots from Room Temperature to 700°C

2015 ◽  
Vol 35 ◽  
pp. 11-20 ◽  
Author(s):  
Zi Yan Zhao ◽  
Ying Zhou ◽  
Feng Gang Bian ◽  
Kun Hao Zhang
Keyword(s):  
Quantum Dots ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Room Temperature ◽  
Cdse Quantum Dots ◽  
Cdse Qds ◽  
In Situ Xafs

In this paper, we synthesized the CdSe quantum dots (QDs) about 4.5 nm, and using the in-situ XAFS technique to study the thermal expansion of CdSe QDs from room temperature to 700°C. We find that the thermal expansion of the CdSe QDs is about 2.0×10-5/K, which is bigger than the bulk CdSe (3~8×10-6/K). This can demonstrate that the thermal properties of CdSe QDs is related to the size of the dots, which means the thermal expansion is reducing as the size of the nanoparticles increasing. Keywords: CdSe quantum dots, thermal expansion, EXAFS technique

scholarly journals The replusive forces between isotopic molecules

1940 ◽  
Vol 174 (959) ◽  
pp. 504-509 ◽  
Keyword(s):  
Zero Point ◽  
Electron Shell ◽  
Intermolecular Forces ◽  
Zero Point Energy ◽  
Restoring Force ◽  
Point Energy ◽  
Nuclear Masses ◽  
Energy Of Interaction ◽  
The Difference ◽  
Made In

It is usually assumed that the forces of attraction and repulsion between two molecules depend only on their electronic structures and are independent of the nuclear masses. While this assumption is undoubtedly true to a first approximation it fails to take into account the zero-point energy associated with the nuclear vibrations, which will modify the charge distribution both of the nuclei and of the electronic shells. Since the zero-point energy depends upon the nuclear mass, this may lead to differences between the behaviour of a pair of isotopic molecules such as H 2 and D 2 . If the restoring force of the nuclear vibration is not directly proportional to the displacement of the nuclei from their mean position, then the mean internuclear distance will be different for the two isotopes. The magnitude of this anharmonic effect can be calculated from spectrum data, and it is found that for H 2 and D 2 the difference is less than 10 -11 cm., and hence negligible. However, the energy of interaction of two molecules will not be a linear function of the inter­ nuclear distance within the molecules, so that even for harmonic oscillations the observed interaction will depend upon the magnitude of the zero-point energy. Both the attractive and the repulsive intermolecular forces will be affected in this way, but it is difficult to treat the former owing to the absence of any exact treatment of exchange forces between molecules. The problem is more easily attacked in the case of the Coulomb forces (which have a net repulsive effect), and the present paper constitutes an attempt to estimate the isotope effect for this type of force. It will be necessary to neglect the mutual deformation of the charge distributions caused by the approach of the two molecules. This assumption is usually made in dealing with Coulomb forces, and it is unlikely to introduce serious error in calculating the isotopic difference. The total Coulomb interaction between two molecules can then be written as G = G n + G n c + G e (1) where G n is the interaction between the nuclei of the two molecules, G ne the interaction between the nuclei of one molecule and the electron shell of the other, and G e the interaction between the two electron shells. The principles involved are most easily seen by considering G n for two diatomic molecules.

scholarly journals Dispersion of Phonons in Ideal Crystals

1969 ◽  
Vol 22 (4) ◽  
pp. 471 ◽  
Author(s):  
NP Gupta
Keyword(s):  
Experimental Data ◽  
Phonon Dispersion ◽  
Zero Point ◽  
Lattice Vibrations ◽  
Rare Gases ◽  
Point Energy ◽  
Phonon Dispersion Curves ◽  
Debye Theory ◽  
Specific Heats ◽  
Theoretical Frequency

A quasiharmonic central force rigid-atom model has been used to study the lattice vibrations of frozen rare gases. The model takes care of interactions up to fourth neighbour and estimates zero-point energy and its volume derivatives by the Debye theory of specific heats. The theoretical frequency distribution and phonon dispersion curves are found to compare reasonably well with the available experimental data. Various causes of the discrepancies and possibilities of improvement of the results are discussed.

scholarly journals Structure and thermal properties of crystals, VI. The role of hydrogen bonds in Rochelle salt

1946 ◽  
Vol 185 (1003) ◽  
pp. 448-465 ◽  
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Curie Point ◽  
Rochelle Salt ◽  
Transition Range ◽  
X Ray ◽  
Short Hydrogen Bonds

X-ray measurements have been made of changes in the lattice spacings of Rochelle salt between —90 and +40° C. Rough visual estimates have also been made of changes in the intensities of X-ray reflexions with temperature. The thermal properties of Rochelle salt have been correlated with its crystal structure. As with other crystals containing hydrogen bonds, thermal expansion is largest in the direction of these bonds, but above the upper Curie point this predominance largely disappears. Between the two Curie points the thermal expansion shows anomalies and is subject to hysteresis. Two main theoretical problems are discussed in the light of the observations. In the first place, the thermodynamic changes at the lower and upper Curie points have hitherto appeared to be transitions ‘of the second kind’, occurring within single crystals without change of phase. Fresh X-ray evidence shows that over the transition range of temperatures measurable differences can be detected between subcrystalline domains within a ‘single’ crystal. These differences reach a maximum value in certain directions in the crystal, but appear to be insufficient to cause it to break up into powder, with change of phase, at the two Curie points, so that most of the properties of a single crystal are retained over the whole range of temperatures. The experimental conclusions throw light on the general theory of phase transitions of the second kind. Secondly, the onset of anomalous dielectric properties at the lower Curie point is ascribed to the stretching of short hydrogen bonds owing to the thermal expansion of the crystal. This changes the bonds from a non-polar to a polar character and is correlated with thermal effects in other crystals containing hydrogen bonds. In extension of apparatus previously described a new controlled temperature chamber has been devised, which has been used with various X-ray cameras for single crystal work at temperatures down to — 90° C.

A NOVEL DIELECTRIC CERAMIC FOR MICROWAVE PASSIVE CIRCUITS

2013 ◽  
Vol 22 ◽  
pp. 153-158 ◽  
Author(s):  
JOBIN VARGHESE ◽  
MATHEU PRESUME ◽  
KUZHICHALIL PEETHAMBHARAN SURENDRAN ◽  
MAILADIL THOMAS SEBASTIAN
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Room Temperature ◽  
Dielectric Ceramic ◽  
Microwave Frequencies ◽  
State Ceramic ◽  
Solid State Ceramic Route ◽  
Ceramic Route ◽  
First Time

The tetragonal Ca 9 Nd 2 W 4 O 24 (CNW) ceramic was prepared by the conventional solid state ceramic route and their dielectric properties were investigated in the radio and microwave frequencies. The CNW ceramics sintered at 1450 °C for 4 h showed a densification 92 % with εr = 16 and tanδ = 0.004 at 15.1 GHz. The thermal conductivity of ceramic at room temperature was found to be 1.6 W m−1K−1 and coefficent of thermal expansion of CNW ceramics was 4.2 ppm/°C measured in the range of 25 to 600 °C. The dielectric and thermal properties of CNW ceramic are reported for the first time.

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