Bond Length Distribution Research Articles

The effect of B2O3 on the structure and properties of titanium slag melt by molecular dynamics simulations

Synthetic rutile was prepared from titanium slag melt with a low amount of additive (B 2 O 3 ) and low energy consumption in our previous work. The mechanism by which B 2 O 3 promotes the precipitation of the rutile phase during the cooling and crystallization of titanium slag melt is not clear and needs further theoretical study. The effects of B 2 O 3 on the structure and properties of titanium slag melt were investigated by molecular dynamics simulations in this study. The B 2 O 3 content has a remarkable effect on the coordination environments of B, Ti and Si atoms, while it has no distinct effect on the position of the central peak in the bond length distributions of BO p , TiO m and SiO n polyhedra. As the B 2 O 3 content increases from 0% to 24%, some of the Ti–O bonds in the oxygen connections are replaced by the B–O bonds and the structural strength of the titanium slag melt is reduced. As the B 2 O 3 content increases from 0% to 24%, the self-diffusion coefficients of all ions increase, and their order remains the same. As the B 2 O 3 content increases from 0% to 24%, the viscosity of the titanium slag melt decreases from 0.079 to 0.032 Pa·s. The addition of B 2 O 3 reduces the overall strength, increases the diffusion coefficients and decreases the viscosity of the titanium slag melt. Such changes are conducive to the oxidation of low-valent titanium and to the precipitation of rutile in titanium slag melt. This work may lay the foundation for the efficient preparation of synthetic rutile by adding B 2 O 3 to the titanium slag melt.

Mechanistic studies of carbocycles on elemental mercury adsorption on carbonaceous surface

Multiple-membered carbocycle (MMC) is a potential material to modify activated carbon for mercury removal in coal-fired power plants due to its unique effect on carrier properties. Density functional theory (DFT) method was utilized for the first time to reveal the effect of MMC on elemental mercury adsorption on the carbonaceous surface. The calculation results indicate that the distribution of CC bond lengths presents two different trends due to the influence of MMC. Then, all mercury-containing models are divided into three categories based on the mercury position and adsorption energy. The adsorption energy can reach the maximum value only when the mercury is co-adsorbed by substrate surface and MMC, such as Model C(B), D(B) and I(T&B). The Mulliken charge population implies that the four-membered carbocycle is capable to repel electrons, which can be regarded as an effective tool for charge rearrangement. In addition, the magnitude of charge transfer directly determines the adsorption energy, which is reflected in the order of three categories. The partial density of state (PDOS) and HOMO-LUMO energy gap analyses show that the adsorption energy of the second and third categories increases as the number of carbon atoms on MMC increases.

Vibrational properties of graphene quantum dots: Effects of confinement, geometrical structure, and edge orientation

We perform ab initio density functional theory calculations to study the lattice vibrations of graphene quantum dots (GQDs) with triangular, quadrate, and hexagonal shapes in lateral confinement of 1 to 3 nm and terminated in both zigzag and armchair orientations. We see the vibrational properties of GQD transform from molecular type into bulk-like type with increasing dot size and the features of the vibrational density of state also highly depend on the symmetry of the GQD. We find that the out-of-plane vibrated standing waves induced by lateral confinement instead of the in-plane vibrations dominate the lattice vibrations of small GQDs. By projecting the vibrational eigenvectors of GQDs on those of single-layer graphene, we see the mixture of the out-of-plane and in-plane vibrational characters in GQDs as the result of the strong lateral confinement. We identify coherent acoustic phonon modes in GQDs and find that the size dependence of coherent acoustic phonon frequency increases with increasing the isotropy of nanostructures. Moreover, different confinement effects on lattice vibrations along zigzag and armchair edge orientations are identified from ab initio calculations. We describe the Raman intensity of GQDs and observe a blue shift of the G-mode position in GQDs comparing to that of the single-layer graphene. Combining the bond length distribution at the edge of GQDs with the positive Gr\"uneisen parameters, we link such blue shift to the surface effect of GQDs.

Structural, textural, and chemical controls on the OH stretching vibrations in serpentine-group minerals

Abstract. The OH stretching vibrational properties of eight serpentine samples from veins of the New Caledonian ophiolite have been investigated by Fourier-transform infrared spectroscopy (FTIR) in the mid-infrared and near-infrared ranges and by Raman spectroscopy. The samples were selected for their monophasic composition (Lz: lizardite; Ctl: chrysotile; and Atg: antigorite) making them representative of the three serpentine species. Comparison of fundamental and overtone spectra allowed us to interpret most of the observed bands and to propose consistent spectral decomposition in individual components. The OH stretching bands related to intrinsic vibrational properties of the minerals are distinguished from those associated with chemical substitutions in octahedral sites (mainly Fe and Ni for Mg substitutions). Observations made on the most symmetric Lz are consistent with previous interpretations and underline the effect of macroscopic parameters on OH stretching bands in the FTIR spectra. The major importance of the distribution of OH bond lengths in the broadening of the vibrational signals of the less symmetric and more distorted Atg is confirmed. The combination of the three spectroscopic methods makes it possible to unravel the occurrence of two different types of interlayer OH environments in Ctl nanotubes. One corresponds to the features observed at 3684 and 7171 cm−1 in the fundamental and overtone spectra, respectively, and is similar to the local OH environment observed in Lz. The other corresponds to broader signals observed at 3693 and 7200 cm−1 in the fundamental and overtone spectra, respectively. It reflects a distribution of OH bond lengths likely related to local structural misfits between adjacent layers in the tubular structure of Ctl.

Analysis of Biphenylene and Benzo{3,4}cyclobuta{1,2-c}thiophene Molecular Orbital Structure using the Huckel Method

The Huckel method is an old fashion method to predict the molecular orbital and energies of  electrons in a conjugated molecule. Although Huckel`s theory`s approximations are relatively crude, its general results are still reasonable compared to the advanced computing method and experimental results for many molecules. This paper describes the Huckel calculation of biphenylene and benzo{3,4}cyclobuta{1,2-c}thiophene using the HuLis software. The benzo{3,4}cyclobuta{1,2-c}thiophene is a derivative of biphenylene, in which case one of the benzene rings is replaced by a thiophene ring. This change produces new electronic properties that are interesting to study. This work focused on calculating those molecules on energy levels diagrams, linear combination coefficient of molecular orbitals, molecular orbital shape, energy gap, resonance energy, bond-order, bond length, and charge distribution (π electron population). Besides, we calculate the harmonic oscillator measure of aromaticity (HOMA) parameter to study the Huckel method`s validity.

Ab initio study of local lattice distortion of hexagonal closed-packed high-entropy (Mo0.25Nb0.25Ta0.25V0.25) (Al0.5Si0.5)2 and the influence on thermodynamic property

High-entropy ceramics have been increasingly attracting great attention due to their novel properties and widespread applications. In this paper, the local lattice distortion (LLD) of hexagonal closed-packed high-entropy (MoNbTaV) (AlSi)2 and the influence on thermodynamic properties are studied using density functional theory and special quasi-random structure for modelling the chemical disorder. The comparative study between pristine and distorted structures shows that LLD improves the stability and ductility of (MoNbTaV) (AlSi)2, in spite of the little effect on lattice constants. Then LLD is quantified in terms of the standard deviation of statistical distribution of bond lengths. The results show that in (MoNbTaV) (AlSi)2, the LLD in the intra-layer is obviously stronger. Moreover, the influence of LLD on electronic structure is further studied, showing that the larger DOS at EF may be correlated with the larger LLD. The Fermi level of distorted structure is closer to the bottom of pseudogap, and the TDOS at Fermi level decreases significantly, so the LLD stabilizes the structure. Especially, the effect of LLD on thermodynamic properties is deeply investigated. Stemming from the normal high-temperature softening of vibration of LLD, thermodynamic entropy is larger, the thermal expansion is stronger, and the heat capacity is enhanced particularly at low temperature. The present study shows that the stability, ductility and thermodynamic properties can be adjusted by LLD, so is valuable for the understanding and designing of the multi-anionic high-entropy ceramics.

The structure of sodium silicate glass from neutron diffraction and modeling of oxygen‐oxygen correlations

AbstractIt is shown that modeling the first oxygen‐oxygen peak in the neutron correlation function of a glass enables structural information about other correlations to be obtained, and the method is illustrated by application to a sodium silicate glass. The first O–O coordination number can be calculated from network theory, and sodium silicate crystal structures show that the mean O–O distance can be calculated from the Si–O distance, despite the distortion of the SiO4 tetrahedra. Modeling the O–O peak for a sodium silicate glass allows the Na‐O bond length distribution to be determined. For a binary glass with 42.5 mol% Na2O, it is found that the Na–O coordination number is 4.8(2) with an average bond length of 2.45 Å, and the Na–O bond lengths are more widely distributed than in sodium silicate crystal structures. Sodium ions are bonded mostly to non‐bridging oxygens (NBOs), and the Na–NBO coordination number may be four as in crystals. Sodium ions are also bonded to a smaller number of bridging oxygens (BOs). Contrary to previous reports, it is not concluded that Na–NBO bonds are shorter than Na–BO bonds, but instead that the Na–BO distribution is relatively narrow, whilst the Na–NBO distribution extends to both shorter and longer distance. The broad distribution of Na–O bond lengths arises from a relatively broad distribution of Na–NBO bond valences, subject to the overall requirement of charge balance.

Intrinsic mechanical properties of hexagonal multiple principal element alloy TiZrHf: An ab initio prediction

The mechanical properties of novel hexagonal close-packed medium entropy alloy TiZrHf have been studied using first-principles method based on special quasi-random structure. The elastic properties and stress-strain relations of unitary Ti, Zr, Hf, binary alloys TiZr, TiHf and ZrHf have also been studied to benchmark the calculation accuracy. The derived elastic constants suggest the mechanical stability of TiZrHf alloy and all three binary alloys. The elastic constants of TiZrHf indicate a weak strengthening effect. Relatively, TiZrHf has larger strength and stiffness, and also exhibits small elastic anisotropy from several criteria. Especially, ideal strength is further studied. The ideal tensile strength (ITS) of TiZrHf along with all unitary and binary materials takes place in the [112¯0] direction. The ITS of TiZrHf is 3.87 GPa and the corresponding critical tensile strain is 0.08. The ideal shear strength (ISS) for all studied materials occurs in the (101¯0) <112¯0> shear system. The obtained ISS τ{10-10}[11-20] for TiZrHf is 2.11 GPa at critical strain of ~0.09. The initial slopes of tensile and shear stress - strain curves correspond well to the tensile Young's modulus and shear modulus computed from elastic constants. Moreover, the resolved shear stress estimated from the ITS is smaller than the ISS τ{10-10}[11-20] for each calculated alloy, indicating that the studied alloys are preference to shear slip before tensile failure. From shear stress-stain relation, the intrinsic shearability and half-width of the dislocation core are also studied for all calculated alloys. Then the inherent mechanism of mechanical properties of TiZrHf is further studied by examination of the detailed bond length distribution and the charge density distribution evolution. At critical point under tensile loading, the simultaneous breakdown of bonds results in a steep drop in tensile stress due to homogeneity. Whereas gradual breakdown of chemical bonds under shear deformation is predicted.

Motion of a polymer globule with Vicsek-like activity: from super-diffusive to ballistic behavior

ABSTRACT Via molecular dynamics simulation with Langevin thermostat we study the structure and dynamics of a flexible bead-spring active polymer model after a quench from good to poor solvent conditions. The self propulsion is introduced via a Vicsek-like alignment activity rule which works on each individual monomer in addition to the standard attractive and repulsive interactions among the monomeric beads. We observe that the final conformations are in the globular phase for the passive as well as for all the active cases. By calculating the bond length distribution, radial distribution function, etc., we show that the kinetics and also the microscopic details of these pseudo equilibrium globular conformations are not the same in all the cases. Moreover, the center-of-mass of the polymer shows a more directed trajectory during its motion and the behavior of the mean-squared-displacement gradually changes from super-diffusive to ballistic under the influence of the active force in contrast to the diffusive behavior in the passive case.

Crystal Structures of Tetramesityl‐Substituted Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene

AbstractCrystal structures of tetramesityl‐substituted tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP) derivative were determined for crystals containing different solvents, CHCl3, CH2Cl2, acetone, and benzene at different temperatures to discuss the conjugation modes in the antiaromatic system, i. e., whether it adopts a D2h structure consisting of local aromatic sextets and quinodimethane substructures or a D4h double annulenenoid structure. The structures of the TCPTP core in all crystals determined at 113 K or 93 K resemble those of the theoretical D2h geometry, whereas the bond lengths at room temperature (293 K) adopt averaged values of the theoretical D2h and D4h geometries. These results are interpreted in terms of disorder of two perpendicularly oriented D2h structures at room temperature and support the theoretical prediction which favours the D2h geometry. The slightly different bond length distributions in the crystals are ascribed to the different space in the vicinity of the molecule which allows the molecule to adopt the two orientations in different occupancies.

Theoretical studies on CL-20/HMX based energetic composites under external electric field

The response of various CL-20 and HMX based energetic composites to external electric field was studied by molecular dynamics simulations. The results indicate that structural features, energetic properties and mechanical properties of all energetic systems show great dependence on the additives, ratio of CL-20 to HMX and external electric field. The comprehensive analysis about structural features based on trigger bond length distribution, the maximum bond length of trigger bond and radial distribution functions between O and H atoms suggest that additives, ratio of CL-20 to HMX, and external electric field can effectively adjust and improve the stability for the energetic systems. The discussions about energetic properties based on potential energies, cohesive energy density and interaction energy between two N atoms of N-N trigger bond reveal that stability of the energetic systems can be adjusted by adding additives and changing ratio of CL-20 to HMX, and can be enhanced by the introduction of external electric field. Besides, the studies show that mechanical properties can be significantly adjusted and improved by the proportion of main explosives, additives and an external electric field. Our studies may provide an avenue to adjust and improve the performances of energetic materials.

External electric field induced conformational change and improved stability for series of energetic pentazole anion salts: A theoretical study

The structural features, energetic characteristics, and dynamics behaviors for series of pentazole anion salts under various intensities of external electric field (0.0–0.5 V/Å) were investigated by molecular dynamics simulations. The results show that there exist significant conformational changes for (NH4)N5 in 0.2 V/Å and [N(CH3)4]N5 in 0.5 V/Å. The sudden conformational changes resulted in sudden changes in energetic properties, dynamics behaviors, and so on. The comprehensive analysis on N-N bond length distribution, potential energy and cohesive energy density indicates that external electric field can improve thermodynamics stability. The analysis on diffusion behavior suggests that external electric field restrict the diffusion of N5− anion. Our studies innovatively introduced external electric field by Perl script and provide a new avenue to tune and improve the performances of energetic materials by external electric field.

Influence of Local Lattice Distortion on Elastic Properties of Hexagonal Close‐Packed TiZrHf and TiZrHfSc Refractory Alloys

The unique mechanical properties and local lattice distortion (LLD) for hexagonal close‐packed (HCP) multiple principal element alloys (MPEAs) are very rarely studied so far. Employing density functional theory calculation based on special quasirandom structure, this work studies the influences of LLD on elastic properties for both novel hexagonal TiZrHf(Sc) MPEAs. Compared to the pristine structures, the lattice stability of distorted random structures is improved evidently. Moreover, LLD obviously lessens the shear elastic properties, which may be an ubiquitous phenomenon irrespective of the lattice types of MPEAs. These results also uncover the apparent improvement in malleable behavior and shear anisotropy for HCP MPEAs. So, the influence of LLD on elastic properties for HCP MPEAs is profound. The degree of LLD is further studied via the standard deviation of near‐neighbor (NN) and next NN bond length distributions as an effective indicator of LLD. More significant distortion uncovered in TiZrHf alloy corresponds consistently to the stronger effects of LLD in TiZrHf alloy. Bader's charge and charge density distribution also demonstrate the underlying impact on LLD for both HCP MPEAs, so electronic nature is a significant factor for LLD. The present study provides guideline for designing mechanical properties of TiZrHf‐based HCP MPEAs engineering materials.

The crystal structure of Tl2.36Sb5.98As4.59S17, the lead-free endmember of the chabournéite homeotypic group

ABSTRACT The crystal structure of Tl2.36Sb5.98As4.59S17, the lead-free endmember of the chabournéite homeotypic group, from the Tl-As-Sb-rich gold deposit at Vorontsovskoye (the Urals, Russia) was determined and refined to R(obs) 0.099 for 9340 unique observed X-ray reflections. The triclinic unit-cell parameters determined from single-crystal data are as follows: a = 8.63253(19) Å, b = 16.3055(7) Å, c = 21.8196(8) Å, α = 75.094 (3)°, β = 83.631(2)°, γ = 89.303 (2)°, V = 2949.18(18) Å3 (Z = 4), space group . The crystal structure is composed of (001) slabs based on PbS and SnS archetypes, arranged in regular alternation. All Sb(As) coordination polyhedra are (Sb,As)S3+2+(1 or 2) coordination pyramids, in the majority of cases with a mixed Sb-As occupancy in both slab types. Bond-length distributions were studied in detail. The zig-zag boundary between the slabs is composed of a repeating sequence of [100] Tl-Tl, Sb-Sb (1/3 substituted by As), Tl-Tl, and Tl-Sb columns. Thallium forms tricapped trigonal coordination prisms and (Sb,As) forms bicapped prisms. Differences compared to two related structures—parapierrotite and tsygankoite—are specified. Twinning of chabournéite is connected with the (imperfect) order-disorder character of the structure, which is connected with the configurations observed on slab boundaries. The structure refinement of the lead-free Tl-(Sb,As) chabournéite endmember presented in this paper is the best starting point for a restudy of all complexities of the chabournéite homeotypic group.

Twisted helical armchair graphene nanoribbons: mechanical and electronic properties

The Hydrogen and Fluorine planar armchairs graphene nanoribbons (H & F AGNRs), subjected to twist deformation within fixed periodic boundary conditions. H-AGNRs is highly elastic in nature, though passivation with Fluorine does induce the plasticity when twisted beyond threshold torsional strain. This plasticity attributes to the wider bond length distribution suggests distortion of benzo-rings. The bandgap response to the effective strain of narrow GNRs $$\varvec{N}=6, 7$$ , and 8 get arranged as (i) monotonously increasing for $$\varvec{q}=0,2$$ and (ii) decreasing for $$\varvec{q}=1$$ ; here, $$\varvec{q}=mod\left( \varvec{N},3 \right) $$ in effective strain space $${{({\varvec{\theta }} }}^{\varvec{2}}\varvec{\varSigma }^{\varvec{2}}\varvec{)}$$ . The effective strain space is found to be more appropriate for gauging the response of torsional strain. This trend has also been observed for Fluorine passivated AGNRs; however, because of higher sensitive response to torsional strain, the bandgap of $$\varvec{N}=$$ 7 F-AGNRs drops from $$\varvec{E}_{\varvec{g}}\simeq 0.95\hbox {eV}$$ to $$ \varvec{E}_{\varvec{g}}\simeq 0.05\hbox {eV}$$ at extreme torsional strain forming Dirac cone at $$\pm \varvec{K}$$ allows dissipationless transport to charge carriers of high kinetic energy at low bias.

Subsurface structural change of silica upon nanoscale physical contact: Chemical plasticity beyond topographic elasticity

Surface defects or flaws on materials made by physical contacts with foreign objects can deteriorate their mechanical properties and limit technical applications. Thus, understanding the contact-induced subsurface damage is of great importance. Using nanoscale infrared spectroscopy and reactive molecular dynamics simulations, the subsurface structural changes of silica upon nanoindentation and nanoscratch are investigated. The results reveal an elongation of the SiO bond length distribution even after the topographically-elastic contact, indicating a “chemical plasticity” at the sub-Angstrom level. In the plastic region with subsurface densification, the SiO bond is found to be slightly longer than the pristine region, indicating the decrease in molar volume is accompanied with the elongation, not shortening, of the SiO bond. These results elucidate the structural damage of a material upon physical contact cannot be delineated based on the topographic deformation of the surface.

Computational analysis the relationships of energy and mechanical properties with sensitivity for FOX-7 based PBXs via MD simulation.

Molecular dynamics (MD) simulations have been applied to investigate 1, 1-diamino-2, 2-dinitroethene (FOX-7) crystal and FOX-7 (011)-based polymer-bonded explosives (PBXs) with four typical polymers, polyethylene glycol (PEG), fluorine-polymer (F2603), ethylene-vinyl acetate copolymer (EVA) and ester urethane (ESTANE5703) under COMPASS force field. Binding energy (Ebind), cohesive energy density (CED), initiation bond length distribution, RDG analysis and isotropic mechanical properties of FOX-7 and its PBXs at different temperatures were reported for the first time, and the relationship between them and sensitivity. Using quantum chemistry, FOX-7 was optimized with the four polymers at the B3LYP/6-311++G(d,p) level, and the structure and RDG of the optimized composite system were analysed. The results indicated that the binding energy presented irregular changes with the increase in temperature. The order of binding ability of different binders to the FOX-7 (011) crystal surface is PEG > ESTANE5703 > EVA > F2603. When the temperature increases, the maximum bond length (Lmax) of the induced bond increases and the CED decreases. This result is achieved in agreement with the known experimental fact that the sensitivity of explosives increases with temperature, and they can be used as the criterion to predict the sensitivity of explosives. The descending order of Lmax is FOX-7 > F2603 > ESTANE5703≈EVA > PEG. The intermolecular interactions between FOX-7 and the four polymers were mainly weak hydrogen bonding and van der Waals interactions, and these interactions helped to reduce the bond length of C-NO2, leading to a decrease in the sensitivity of FOX-7. The addition of polymers can effectively improve the mechanical properties of explosives. Among the four polymers, EVA has the best effect on improving the mechanical properties of FOX-7 (011). At the same temperature, the modulus can be used to predict the sensitivity of high-energy materials. Cauchy pressure can predict the sensitivity of non-brittle energetic materials. The nature of the interaction between FOX-7 and the four polymers is hydrogen bonding and van der Waals force, of which hydrogen bonding is the main one. These studies are meaningful for the formulation design and sensitivity prediction of FOX-7 and its PBXs.

A Phase-Change Mechanism of GST-SL Based Superlattices upon Sb Flipping.

Reversible phase-change behaviors of Ge–Sb–Te based superlattices (GST-SL) were studied by ab initio molecular dynamics (AIMD) simulations based on three models containing Ge/Sb intermixing, namely the Petrov-mix, Ferro-mix, and Kooi-mix models. The flipping behavior of Sb atoms was found in all the three GST-SL models in the melting process. Among them the Kooi-mix model exhibited the best stability, and the analyses of bond length distribution and electron localization function provided a better explanation on the phase transition of GST-SL. Finally, we proposed a fast switching model for GST-SL based on Sb flipping.

Understanding the strain-dependent structure of Cu nanocrystals in Ag-Cu nanoalloys.

The structure of octahedral Ag-Cu nanoalloys is investigated by means of basin hopping Monte Carlo (BHMC) searches involving the optimization of shape and chemical ordering. Due to the significant size mismatch between Ag and Cu, the misfit strain plays a key role in determining the structure of Ag-Cu nanoalloys. At all the compositions, segregated chemical ordering is observed. However, the shape of the Cu nanocrystal and the associated defects are significantly different. At lower amounts of Cu (as little as 2 atom %), defects close to the surface are observed leading to a highly non-compact shape of the Cu nanocrystal which is non-trivial. The number of Cu-Cu bonds is relatively lower in the non-compact shape which is contrary to the preference of bulk Ag-Cu alloys to maximize the homo-atomic bonds. Due to the non-compact shape, {100} Ag-Cu interfaces are observed which are not expected. As the amount of Cu increases, the Cu nanocrystal undergoes a shape transition from non-compact to a compact octahedron. The associated defect structure is also modified. The structural changes due to the strain effects have been explained by calculating the atomic pressure maps and the bond length distributions. The trends relating to the structure have also been verified at larger sizes.

Representing molecular ground and excited vibrational eigenstates with nuclear densities obtained from semiclassical initial value representation molecular dynamics.

We present in detail and validate an effective Monte Carlo approach for the calculation of the nuclear vibrational densities via integration of molecular eigenfunctions that we have preliminary employed to calculate the densities of the ground and the excited OH stretch vibrational states in the protonated glycine molecule [Aieta et al., Nat Commun 11, 4348 (2020)]. Here, we first validate and discuss in detail the features of the method on a benchmark water molecule. Then, we apply it to calculate on-the-fly the ab initio anharmonic nuclear densities in the correspondence of the fundamental transitions of NH and CH stretches in protonated glycine. We show how we can gain both qualitative and quantitative physical insight by inspection of different one-nucleus densities and assign a character to spectroscopic absorption peaks using the expansion of vibrational states in terms of harmonic basis functions. The visualization of the nuclear vibrations in a purely quantum picture allows us to observe and quantify the effects of anharmonicity on the molecular structure, also to exploit the effect of IR excitations on specific bonds or functional groups, beyond the harmonic approximation. We also calculate the quantum probability distribution of bond lengths, angles, and dihedrals of the molecule. Notably, we observe how in the case of one type of fundamental NH stretching, the typical harmonic nodal pattern is absent in the anharmonic distribution.