Longitudinal Splitting Research Articles

Dispersion and density of states of phonons and electrons in an α-B12 crystal determined from first principles

Using the DFT method, we study the phonon properties of an α-B12 rhombohedral crystal in the basis set of plane waves and its electronic structure in the localized basis set of Gaussians. It follows from the phonon dispersion that the crystal possesses a dynamical stability. The effective Born charges, the oscillator strengths, the transverse–longitudinal splitting, and the dielectric functions of dipole modes are calculated. We show that charge transfer from polar to equatorial atoms takes place in a В12 icosahedron, while В–В bonds have predominantly a covalent character. In the density of states of acoustic modes, we reveal a structure that can manifest itself in the spectra of disordered boron compounds. From the dispersion of electronic bands, the occurrence of an indirect energy gap follows. The overlap of partial densities implies the hybridization of s and p electronic states in boron atoms.

Experimental investigation on the behavior of glued-in rod joints in timber beams subjected to monotonic and cyclic loading

Glued-in rod connections for timber beams are increasingly being used, as they offer high strength and stiffness and a better appearance in comparison with traditional mechanical connections. First, a campaign of experimental tests on glued-in threaded steel rod joints subjected to monotonic bending moments was carried out, checking the effect of a confining system for the bars (transversal screws) and the different arrangement of the rods, or varying the mechanical characteristics of the steel of the bars. A negligible effect on joint ductility was observed using transversal screws whereas with a correct design and a proper choice of rod steel grade an important ductile behavior was achieved. The experiments were then extended to cyclic tests so to emphasize the cyclic performance of glued-in rod joints under bending moments. The aim was mainly to understand the joint structural response under cyclic loads, simulating the effects of seismic action. The test results indicate that the joint can initially develop a high dissipative capacity, but after a few cycles, the energy dissipation is considerably reduced by the occurrence of longitudinal splitting in the timber edge of the joining bars leading to lateral instability of the rods.

Design and experimental verification of easily constructible bamboo footbridges for rural areas

The present study examines a new approach for low-cost footbridges as a remedy to the overwhelming lack of bridges in underprivileged rural areas. The proposed truss footbridges can be rapidly assembled, by non-experienced personnel from pre-fabricated full culm bamboo members and steel gusset plate type connections. This paper addresses the challenges of the design and the construction, and highlights important knowledge gaps in the process. Firstly, it evaluates experimentally the physical and mechanical properties of bamboo culms from two species (namely, Kao Jue and Mao Jue). Then, it develops an analytical model and performs the structural design of the bridge. Importantly, the present study introduces a new three-dimensional gusset plate type truss connection for full culm bamboo members. The proposed connection overcomes the assembly problems due to the non-standardized bamboo geometry. The study also reports the construction of full scale bridge prototypes and their experimental testing. The measured deck deflections under vertical loads are reasonably well captured by the analytical model. However, the bridge collapse is due to a local mode failure peculiar to bamboo; longitudinal splitting. The results reveal that the connections and the associated local failure modes of bamboo, are the most sensitive part of the examined structures, and highlight several directions for further experimental and theoretical research.

Terahertz Dielectric Response of Nonpolar a-plane GaN Films

The generation and the detection of the THz radiation in the frequency range of 0.1 to 10 THz have attracted much research interest, which was mainly driven by the particular applications of THz time-domain spectroscopy (TDS) in physics, chemistry, nano and life sciences. THz TDS has shown many advantages due to its non-destructive analysis feature in characterizing complex dielectric properties and understanding the carrier-dynamics in various semiconductor materials. Extensive studies have been reported on the THz dielectric and optical properties such as electro-optical effects, optical rectification, and birefringence. In addition, the ultrafast relaxation and recombination dynamics of photogenerated carriers were investigated for new materials such as carbon nanotube, graphene, and perovskites using optical pump THz-probe spectroscopy. Recently, the terahertz (THz) quantum cascade lasers and intersubband transition devices has attracted considerable attention based on AlGaN/GaN quantum well structure for far-infrared applications. It is necessary to investigate the optical and dielectric properties of GaN and sapphire crystals in the far IR as well as THz frequency regions. In the previous report, nonpolar and semipolar GaN crystals in the hexagonal crystal system are found to show multi-phonon mode behavior in the far-infrared frequency region. In addition, the polarized IR reflectance response of sapphire is reported to exhibit the dependence on the crystal orientation. In this paper, we investigated the optical properties and dielectric response of nonpolar a-plane GaN (a-GaN) films in the terahertz (THz) frequency using polarized femto-second THz TDS. The phase separation and amplitude ratio were measured by changing the crystal orientation with respect to the polarization of the incident THz pulse. In sharp contrast with polar c-plane GaN, nonpolar a-GaN films exhibited the angle dependence of the THz absorptions at room temperature, presumably due to the birefringence in nonpolar a-GaN films. The transmitted THz signal intensity, the time delay, and the Fourier-transformed amplitude were investigated by rotating the azimuth angle of the crystal orientation. Strong THz field absorptions around 1 THz frequency were observed at the azimuth angle of 0°, 90°, and 180° for a-GaN films. We believe that the birefringence in the THz frequency region originates from the difference of the transverse-optical and the longitudinal optical phonon splitting between the optical phonon branches.

Cyclic tests on slip resistance of squat heavyweight concrete shear walls with construction joints

The objective of this study was to examine the effectiveness of different slip-resistance bars (X-, W-, and Ω-shaped bars) on reducing sliding shear displacement at the base interface of squat heavyweight concrete (HWC) shear walls with construction joints. In addition, the structural applicability of welded wire fabric (WWF) reinforcement was investigated as an alternative to the individual deformed bars conventionally used for the shear reinforcement of shear walls. All the wall specimens had the same concrete dry density of 3380kg/m3, geometrical dimensions with barbell-shaped cross-sections, and shear ratio of 1.0. The ultimate failure of the walls subjected to under constant axial loads and reversed cyclic lateral loads was associated with a kinking in the longitudinal and vertical shear bars and splitting of the surrounding concrete at the base interface due to the dowel resistance of the bars. The slip-resistance bars were effective in reducing the shear slip displacement at the base interface after the peak load of the walls was reached. The WWF reinforcement performed comparably to the conventional shear reinforcements in enhancing the shear strength of the squat shear walls and preventing a rapid decrease in the applied loading after the peak strength. The shear strength of the squat HWC shear walls can be conservatively estimated using equations proposed by EC8 for earthquake resistance, even for avoiding sliding shear failure at high wall drift ratios.

Failure mechanism of hollow tree trunks due to cross-sectional flattening.

Failure of hollow trees in urban areas is a worldwide concern, and it can be caused by different mechanisms, i.e. bending stresses or flattening-related failures. Here we derive a new analytical expression for predicting the bending moment for tangential cracking, and compare the breaking moment of various failure modes, including Brazier buckling, tangential cracking, shear failure and conventional bending failure, as a function of t/R ratio, where t and R are the trunk wall thickness and trunk radius, respectively, of a hollow tree. We use Taiwan red cypress as an example and show that its failure modes and the corresponding t/R ratios are: Brazier buckling (Mode I), tangential cracking followed by longitudinal splitting (Mode II) and conventional bending failure (Mode III) for 0 < t/R < 0.06, 0.06 < t/R < 0.27 and 0.27 < t/R < 1, respectively. The exact values of those ratios may vary within and among species, but the variation is much smaller than individual mechanical properties. Also, shear failure, another type of cracking due to maximum shear stress near the neutral axis of the tree trunk, is unlikely to occur since it requires much larger bending moments. Hence, we conclude that tangential cracking due to cross-sectional flattening, followed by longitudinal splitting, is dominant for hollow trunks. Our equations are applicable to analyse straight hollow tree trunks and plant stems, but are not applicable to those with side openings or those with only heart decay. Our findings provide insights for those managing trees in urban situations and those managing for conservation of hollow-dependent fauna in both urban and rural settings.

EVALUATION OF THE MICROHARDNESS OF ROOT CANAL DENTIN AFTER DIFFERENT IRRIGATION PROTOCOLS (IN VITRO STUDY)

INTRODUCTION: Different irrigations solutions may cause alteration in the physicochemical properties of dentin structure thereby affecting the microhardness of root canal dentin. OBJECTIVES: to evaluate the effect of different irrigation protocols on microhardness of human root canal dentin. MATERIALS AND METHODS: Forty extracted single rooted lower premolars were used. All teeth were instrumented using manual stainless steel files and irrigated by 2ml distilled water between each file, then were sectioned by longitudinal splitting of each tooth. The root halves were randomly assigned into 4 parallel groups (n=10) and immersed for 5 minutes with one of the following irrigants: Group I: 10 ml of 2.5% Sodium Hypochlorite (NaOCL), Group II: 10 ml of 17% ethylene diamine tetra-acetic acid (EDTA) followed by 10 ml of 2.5% NaOCL, Group III: 10 ml of 2.5% NaOCL followed by 10 ml of 2% chlorhexidine digluconate (CHX), Group IV: 10 ml of 2.5% NaOCL followed by 10 ml distilled water then were followed by 10ml of 2% CHX. Ten root halves from each group were prepared to measure dentin microhardness at baseline measurement and after treatment to determine the change in microhardness, using Vickers tester. RESULTS: Data were analysed using t-test, ANOVA test and Post Hoc test.Group II showed the highest percentage decrease in microhardness values, followed by group III, then group IV and the lowest was group I. All groups showed a significant difference between each other (P < 0.05), except group III and IV. The coronal third showed the highest percentage decrease with significant difference between apical and middle thirds (P < 0.05), in which there was no significant difference between them. CONCLUSIONS: CHX is the best final irrigant if there is excellent intermediate flush for prevention of its precipitation with NaOCL.The coronal third needs conservative approach as it is the most affected third.

Intentional Percutaneous Laceration of the Anterior Mitral Leaflet to Prevent Outflow Obstruction During Transcatheter Mitral Valve Replacement: First-in-Human Experience

ObjectivesThis study sought to use a new catheter technique to split the anterior mitral valve leaflet (AML) and prevent iatrogenic left ventricular outflow tract (LVOT) obstruction immediately before transcatheter mitral valve replacement (TMVR). BackgroundLVOT obstruction is a life-threatening complication of TMVR, caused by septal displacement of the AML. MethodsThe procedure was used in patients with severe mitral valve disease and prohibitive surgical risk. Patients either had prior surgical mitral valve ring (n = 3) or band annuloplasty (n = 1) or mitral annular calcification with stenosis (n = 1). Iatrogenic LVOT obstruction or transcatheter heart valve dysfunction was predicted in all based on echocardiography and computed tomography. Transfemoral coronary guiding catheters directed an electrified guidewire across the center and base of the AML toward a snare in the left atrium. The externalized guidewire loop was then electrified to lacerate the AML along the centerline from base to tip, sparing chordae, immediately before transseptal TMVR. ResultsFive patients with prohibitive risk of LVOT obstruction or transcatheter heart valve dysfunction from TMVR successfully underwent LAMPOON, with longitudinal splitting of the A2 scallop of the AML, before valve implantation. Multiplane computed tomography modeling predicted hemodynamic collapse from TMVR assuming an intact AML. However, critical LVOT gradients were not seen following LAMPOON and TMVR. Doppler blood flow was seen across transcatheter heart valve struts that encroached the LVOT, because the AML was split. Transcatheter heart valve function was unimpeded. ConclusionsThis novel catheter technique, which resembles surgical chord-sparing AML resection, may enable TMVR in patients with prohibitive risk of LVOT obstruction or transcatheter heart valve dysfunction.

Experimental evaluation of longitudinal splitting of bamboo flexural components

Splitting or longitudinal shear failures in full-culm bamboo are a critical limit state when using the material for construction applications. Understanding and quantifying the behaviour must be through standardised test methods for international adoption into building practices to be successful. Current testing procedures only determine an effective flexural strength due to splitting failures. The present study investigates longitudinal shear failure in full-culm Phyllostachys pubescens (Moso) and Bambusa stenostachya (Tre Gai) bamboo flexural specimens through a number of standard and modified test methods. In particular, the paper proposes modifications to ‘standard’ culm flexural tests intended to better capture actual shear-dominated behaviour. Notched specimens were used to better establish relationships between mode I and mode II behaviours. The test results illustrate the significant degree of interaction between mode I and mode II stresses resulting from flexural tests and their associated failures, specifically the significant deterioration of mode II capacity in the presence of even a small amount of mode I stress. It is proposed that a uniform experimental approach using horizontally notched flexural specimens having different shear spans and notch locations would be appropriate to establish a relationship between mode I and II behaviour.

A comprehensive analysis on the longitudinal fracture in the tool joints of drill pipes

Abstract The Longitudinal fractures or splits in tool joint box of drill pipe often occur, because the numbers of deep, directional, extended and horizontal oil wells are increasing. The mechanism of frictional heat check cracking of drill pipe tool joints was discussed in the standard API RP 7G. However, authors have identified that heat check cracking was just one of the cracking initiation mechanism, not crack propagation mechanism. This paper has reviewed 21 cases of this kind of failure analyzed by authors from year 2000 to 2015. Fracture surfaces and mechanical properties have been examined in this paper. It was found that there were various other causes of crack initiation, in addition to frictional heat check cracking, such as tong tooth bite marks and friction damage in internal threads. Such cracks propagated mostly via stress corrosion cracking (SCC) mechanism, although two cases was brittle cracking due to poor material toughness. The stress corrosion mechanism was related to hydrogen sulfide (H2S) or ionic sulfur (S2 −), which came from the degradation of applied thread greases or drilling fluid ingredients. Although heat check cracks and tooth bite marks as crack initiation are common-place, the failure can be prevented through prevention of crack propagation. Failure data showed that although improved transverse material absorbed energy avoided longitudinal brittle cracking of the tool joint, stress corrosion cracking still occurred. The statistical analysis results showed that material hardness was related to the longitudinal cracking of drill pipe tool joints. It was demonstrated that if material hardness was restricted to less than HB310, the crack did not propagate. It was suggested that the material hardness of tool joints box should be revised to HB285–HB310, in addition that the transverse material Charpy absorbed energy of the tool joint should be specified.

Influence of reinforcement ratio on tension stiffening of reinforced engineered cementitious composites

This paper presents an experimental study on the tension stiffening behaviour of reinforced engineered cementitious composites (ECC). In the experimental programme, ten specimens with concentrically placed steel reinforcement were tested under uniaxial tension. The effects of cross section and longitudinal reinforcement ratio on tension stiffening were investigated. Comparisons were made between ECC and concrete in terms of tension resistance and deformation capacity. Experimental results demonstrated that ECC significantly increased the tension resistance of members at both elastic and post-yield stages of longitudinal reinforcement. Multiple cracks with limited widths and spacings propagated along the length of reinforced ECC at the initial stage. Thereafter, a major crack was formed where the strain capacity of ECC was exhausted, and tension force was transmitted by longitudinal reinforcement across the crack. Localised failure at the major crack eventually led to substantially reduced deformation capacity relative to concrete members. Besides, longitudinal splitting cracks were prevented due to better confinement of ECC. Furthermore, the contribution of ECC to tension resistance was quantified by subtracting the force in longitudinal reinforcement from the total force. Finally, the minimum reinforcement ratio required to ensure adequate force transfer over the major crack was calculated so that full ductility of reinforced ECC members in tension could be achieved.

X-ray computed tomography study of kink bands in unidirectional composites

An experimental study on the axial compressive failure of cylindrical unidirectional (UD) carbon fibre-epoxy rods has been performed to better understand kink bands and the relevant damage mechanisms in three dimensions (3D). Post-mortem X-ray micro-computed tomography (micro-CT) imaging has shown that fibre kink bands predominantly all lie within the same plane in a cylindrical rod sample uniaxially compressed without lateral constraint. Kink bands at different stages of development are contained in the damage volume and the geometric parameters of fully developed kink bands are consistent through the damage zone, with a kink-band width ω≈20–320 μm, kink-band angle β≈11–40° and fibre rotation angle Φ (φ+φo)≈18–52°. Fibre failure, longitudinal splitting and matrix micro-cracks within the fibre kink zone are identified by scanning electron microscopy (SEM) and X-ray micro-CT observations. The smallest radius of curvature that corresponds to maximum amount of bending of the unbroken buckled fibres was ∼280μm (40 fibre diameters). Kink-band boundary planes and longitudinal splitting have been extracted and visualised in 3D for the first time.

Supraspinal control of spinal reflex responses to body bending during different behaviours in lampreys.

Spinal reflexes are substantial components of the motor control system in all vertebrates and centrally driven reflex modifications are essential to many behaviours, but little is known about the neuronal mechanisms underlying these modifications. To study this issue, we took advantage of an in vitro brainstem-spinal cord preparation of the lamprey (a lower vertebrate), in which spinal reflex responses to spinal cord bending (caused by signals from spinal stretch receptor neurons) can be evoked during different types of fictive behaviour. Our results demonstrate that reflexes observed during fast forward swimming are reversed during escape behaviours, with the reflex reversal presumably caused by supraspinal commands transmitted by a population of reticulospinal neurons. NMDA receptors are involved in the formation of these commands, which are addressed primarily to the ipsilateral spinal networks. In the present study the neuronal mechanisms underlying reflex reversal have been characterized for the first time. Spinal reflexes can be modified during different motor behaviours. However, our knowledge about the neuronal mechanisms underlying these modifications in vertebrates is scarce. In the lamprey, a lower vertebrate, body bending causes activation of intraspinal stretch receptor neurons (SRNs) resulting in spinal reflexes: activation of motoneurons (MNs) with bending towards either the contralateral or ipsilateral side (a convex or concave response, respectively). The present study had two main aims: (i) to investigate how these spinal reflexes are modified during different motor behaviours, and (ii) to reveal reticulospinal neurons (RSNs) transmitting commands for the reflex modification. For this purpose in in vitro brainstem-spinal cord preparation, RSNs and reflex responses to bending were recorded during different fictive behaviours evoked by supraspinal commands. We found that during fast forward swimming MNs exhibited convex responses. By contrast, during escape behaviours, MNs exhibited concave responses. We found RSNs that were activated during both stimulation causing reflex reversal without initiation of any specific behaviour, and stimulation causing reflex reversal during escape behaviour. We suggest that these RSNs transmit commands for the reflex modification. Application of the NMDA antagonist (AP-5) to the brainstem significantly decreased the reversed reflex, suggesting involvement of NMDA receptors in the formation of these commands. Longitudinal split of the spinal cord did not abolish the reflex reversal caused by supraspinal commands, suggesting an important role for ipsilateral networks in determining this type of motor response. This is the first study to reveal the neuronal mechanisms underlying supraspinal control of reflex reversal.

Longitudinal splitting versus sequential unzipping of thick-walled carbon nanotubes: Towards controllable synthesis of high-quality graphitic nanoribbons

Despite significant efforts to develop ways to produce customized carbon-based nanostructures, facile synthesis of mass graphene/graphitic nanoribbons (GNRs) without losing the intrinsic sp2-structure and properties remains challenging. Here we report that bulk of multi-layered graphitic nanoribbons can be prepared by gas-phase oxidative splitting of multi-walled carbon nanotubes (MWCNTs) using HNO3 vapor. The longitudinal splitting behavior of MWCNTs is substantially dependent on three key factors: the utilization of gaseous oxidant, the use of highly-crystallined carbon nanotubes with larger diameter, and the associated high-pressure conditions. Moreover, this splitting process is evidenced to be edge-selective and nonaggressive as opposed to traditional wet chemical oxidation, for which the obtained GNRs show minimized oxidation level, highly intact crystalline and robust electrical conductance. This study suggests a simple yet effective strategy for producing mass high-quality GNRs.

Hemihypoglossal-Facial Nerve Anastomosis for Facial Nerve Reanimation: Factors that may Influence the Outcome

The purpose of this study was to identify the factors that may influence the results of hemihypoglossal-facial nerve anastomosis (HHFA). The first 28 consecutive patients who underwent HHFA were analyzed. The facial palsy was related to surgically treated vestibular schwannoma (24), facial nerve schwannoma (1), petroclival meningioma (1), brain stem cavernoma (1) and in one case to purely radiosurgically treated vestibular schwannoma (1). The group included 4 patients with Neurofibromatosis type 2 and also four patients after failed radiosurgery. Duration of facial palsy before the procedure ranged from 1 to 21 months (mean 6.5 months) and was longer than 1 year in 6 patients. The procedure was performed in own modification which is a compilation of the technique described by Darrouzet with the longitudinal splitting technique. The clinical follow-up period was at least 1 year. In 26 out of 28 (93%) patients satisfactory outcome (III° House–Brackmann scale) of CN VII function was achieved. In two remaining patients (both with Neurofibromatosis type 2) facial function improved from paresis to IV° according to House – Brackmann Scale. Patient age, sex, initially treated pathology, previous radiosurgical treatment and time from CNVII injury to anastomosis had no influence on final results. HHFA is an effective modality for treatment of facial palsy with acceptable tongue denervation. Suboptimal results were observed only in NF2 group what might be related to difficulties in rehabilitation process due to common hearing problems or due to other cranial nerve deficits.

A new species of Danothrips from Southwestern China (Thysanoptera: Thripidae).

Danothrips salicis sp. n. is described from young leaves of Salix sp. in Southwestern China. This species is similar to D. moundi, D. theifolii and D. trifasciatus, but can be distinguished by the colour of the fore wing, the median longitudinal split on tergite X of females, and in males by the situation of the median short thorn-like setae on tergite IX.

Simulation on size effect of notched quasi-isotropic composite laminates under tensile loading

The formation of longitudinal splitting alleviates the extremely high stress concentration at notch tips of fiber-reinforced composites under remote tension. Theoretical foundation is provided to show that the true stress field along the potential splitting routes can be accurately modelled by inserting cohesive zones in finite element models, such that strength-based criteria can be used to predict damage initiation. Progressive failure analyses are performed to study the in-plane size effect of double-notched quasi-isotropic composite laminates. To capture the stress relief effect of longitudinal splitting during the loading process, surface-based cohesive contacts are introduced along the fiber directions to model the longitudinal splitting. To predict the possible delamination, interface cohesive contacts are also inserted between plies with different fiber orientations. The advantage of the surfaced-based cohesive contact method over the conventional cohesive element method is that it allows different mesh configurations for plies with different fiber orientations. Failure patterns and failure loads predicted by finite element analyses of three scaled composite laminates were compared with experimental results from open literature.

Data-rich characterisation of damage propagation in composite materials

A novel methodology for the synchronised capture of high resolution white-light and infra-red (IR) images during a fatigue test is described. The approach allows digital image correlation (DIC) and thermoelastic stress analysis (TSA) to be applied practically simultaneously without the requirement to pause the cyclic load. The methodology is demonstrated on cross-ply carbon-epoxy specimens that have experienced damage induced by intermediate strain rate loading. Similar undamaged specimens are studied and the results from each compared. Various damage types are identified which include transverse cracking, delaminations and longitudinal splitting. The results are verified using X-ray computed tomography (CT).

The effects of different fibre packing geometries on the transverse matrix strain magnification and fibre strain reduction in uniaxially aligned continuous fibre-reinforced composites

Expressions for transverse matrix strain magnification and fibre strain reduction are derived for square and hexagonal fibre array reinforced composites. Respective transverse matrix and fibre strain magnification and reduction, for the square arrays are shown to be higher for all reinforcing fibre volume fractions than those for the hexagonal arrays. The respective magnification and reduction of the transverse matrix and fibre strains are shown to decrease with increasing values of the ratio of elastic modulus ( Em/ Ef) for both reinforcing fibre arrays. The magnified transverse matrix strains in axially loaded longitudinally aligned continuous fibre-reinforced composites are shown to be higher than the applied longitudinal strains for all square array reinforcing fibre volume fractions and for all hexagonal array reinforcing fibre volumes fractions above 31%. This raises possibilities of longitudinal matrix splitting before interfacial bond failure and transverse matrix failure, in a strain based rather than stress-based failure mode.

DFT Calculations with van der Waals Interactions of Hydrated Calcium Carbonate Crystals CaCO3·(H2O, 6H2O): Structural, Electronic, Optical, and Vibrational Properties.

The role of hydration on the structural, electronic, optical, and vibrational properties of monohydrated (CaCO3·H2O, hexagonal, P31, Z = 9) and hexahydrated (CaCO3·6H2O, monoclinic, C2/c, Z = 4) calcite crystals is assessed with the help of published experimental and theoretical data applying density functional theory within the generalized gradient approximation and a dispersion correction scheme. We show that the presence of water increases the main band gap of monohydrocalcite by 0.4 eV relative to the anhydrous structure, although practically not changing the hexahydrocalcite band gap. The gap type, however, is modified from indirect to direct as one switches from the monohydrated to the hexahydrated crystal. A good agreement was obtained between the simulated vibrational infrared and Raman spectra and the experimental data, with an infrared signature of hexahydrocalcite relative to monohydrocalcite being observed at 837 cm(-1). Other important vibrational signatures of the lattice, water molecules, and CO3(2-) were identified as well. Analysis of the phonon dispersion curves shows that, as the hydration level of calcite increases, the longitudinal optical-transverse optical phonon splitting becomes smaller. The thermodynamics properties of hexahydrocalcite as a function of temperature resemble closely those of calcite, while monohydrocalcite exhibits a very distinct behavior.