
Alexander CroyFriedrich Schiller University Jena | FSU
Alexander Croy
Dr. rer. nat.
About
104
Publications
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Introduction
Alexander Croy currently works at the Institute of Physical Chemistry of the Friedrich-Schiller-Universität Jena, Germany. Alexander does research in Materials Physics, Condensed Matter Physics and Solid State Physics. He is also interested in electronic olfaction and the associated challenges.
Additional affiliations
July 2016 - July 2021
August 2014 - July 2016
June 2011 - August 2014
Publications
Publications (104)
Phononic crystals and acoustic metamaterials are used to tailor phonon and sound propagation properties by utilizing artificial, periodic structures. Analogous to photonic crystals, phononic band gaps can be created, which influence wave propagation and, more generally, allow engineering of the acoustic properties of a system. Beyond that, nonlinea...
We investigate the electromechanical coupling in 2d materials. For non-Bravais lattices, we find important corrections to the standard macroscopic strain - microscopic atomic-displacement theory. We put forward a general and systematic approach to calculate strain-displacement relations for several classes of 2d materials. We apply our findings to...
In order to understand the relation of strain and material properties, both a microscopic model connecting a given strain to the displacement of atoms, and a macroscopic model relating applied stress to induced strain, are required. Starting from a valence-force model for black phosphorous (phosphorene) [Kaneta et al., Solid State Communications, 1...
The existence of flexural modes with a quadratic phonon-dispersion is a distinguishing property of two-dimensional materials and has important consequences for their properties. Here, we deduce theoretically within the harmonic approximation the conditions for which orthotropic two-dimensional materials display a flexural mode. Further, we derive f...
We introduce the MORE-Q dataset, a quantum-mechanical (QM) dataset encompassing the structural and electronic data of non-covalent molecular sensors formed by combining 18 mucin-derived olfactorial receptors with 102 body odor volatilome (BOV) molecules. To have a better understanding of their intra- and inter-molecular interactions, we have perfor...
Transition metal complexes have played crucial roles in various homogeneous catalytic processes due to their exceptional versatility. This adaptability stems not only from the central metal ions but also from the vast array of choices of the ligand spheres, which form an enormously large chemical space. For example, Rh complexes, with a well-design...
The similarity of local atomic environments is an important concept in many machine learning techniques, which find applications in computational chemistry and material science. Here, we present and discuss a connection between the information entropy and the similarity matrix of a molecule. The resulting entropy can be used as a measure of the com...
Controlling site-selectivity and reactivity in chemical reactions continues to be a key challenge in modern synthetic chemistry. Here, we demonstrate the discovery of site-selective chemical reactions on the water surface via a sequential assembly approach. A negatively charged surfactant monolayer on the water surface guides the electrostatically...
The sense of smell is based on sensory detection of the molecule(s), which is then further perceptually interpreted. A possible measure of olfactory perception is an odor independent olfactory perceptual fingerprint (OPF) defined by Snitz et al. We aimed to investigate, whether OPF can distinguish patients with olfactory dysfunction due to COVID-19...
The coupling of different two‐dimensional materials (2DMs) to form van der Waals heterostructures (vdWHs) is a powerful strategy for adjusting the electronic properties of 2D semiconductors, for applications in opto‐electronics and quantum computing. 2D molybdenum disulfide (MoS 2 ) represents an archetypical semiconducting, monolayer thick versati...
Disgust serves to defend the body from the entry of toxins and disease. Central to this function is a strong relationship with the proximate senses of smell, taste, and touch. Theory suggests that distinct and reflexive facial movements should be evoked by gustatory and olfactory disgusts, serving to impede bodily entry. While this hypothesis has r...
Gas identification plays a critical role in characterizing our (chemical) environment. It allows to warn of hazardous gases and may help to diagnose medical conditions. Miniaturized gas sensors, and especially those based on chemiresistive detection mechanisms, have gained rapid development and commercialization in the past decades due to their num...
Olfaction is an evolutionary old sensory system, which provides sophisticated access to information about our surroundings. In particular, detecting the volatile organic compounds (VOCs) emitted during natural and artificial processes can be used as characteristic fingerprints and help to identify their source. Inspired by the biological example, a...
The calculation of the electron–phonon coupling from first principles is computationally very challenging and remains mostly out of reach for systems with a large number of atoms. Semi-empirical methods, like density functional tight binding (DFTB), provide a framework for obtaining quantitative results at moderate computational costs. Herein, we p...
The behavior of electrons during bond formation and breaking cannot commonly be accessed from experiments. Thus, bond perception is often based on chemical intuition or rule-based algorithms. Utilizing computational chemistry methods, we present intrinsic bond descriptors for the Diels–Alder reaction, allowing for an automatic bond perception. We s...
We report here on results of systematic experimental-theoretical investigation of high-order harmonic generation (HHG) in layers of CdSe semiconductor quantum dots of different sizes and a reference bulk CdSe thin film. We observe a strong decrease in the efficiency, up to complete suppression of HHG with energies of quanta above the band gap for t...
The behavior of electrons during bond formation and breaking cannot commonly be accessed from experiments. Thus, bond perception is often based on chemical intuition or rule-based algorithms. Utilizing computational chemistry methods, we present intrinsic bond descriptors for the Diels-Alder reaction, allowing for an automatic bond perception. We s...
The aim of this work is to demonstrate a computational workflow for the generation of cross-linkable viscoelastic polymers and the determination of elastic and hyperelastic properties by means of all-atoms classical molecular dynamics simulations, using polydimethylsiloxane (PDMS) as an example. To improve the computational efficiency of the workfl...
Molecule- and solid-state gears build the elementary constituents of nanoscale mechanical machineries. Recent experimental advances in fabrication technologies in the field have strongly contributed to better delineate the roadmap towards the ultimate goal of engineering molecular-scale mechanical devices. To complement experimental studies, comput...
We report here on results of experimental-theoretical investigation of high-order harmonic generation (HHG) in layers of CdSe semiconductor quantum dots of different sizes and a reference bulk CdSe thin film. We observe a strong decrease in the efficiency, up to complete suppression of HHG with energies of quanta above the bandgap for the smallest...
Breath analysis is an emerging technique in the field of diagnostics. The presence of thousands of gases and volatile organic compounds (VOCs), many of them at part per billion (ppb) concentration levels, require the development of ultrasensitive and selective detection approaches, which pose challenges still trying to be addressed by the scientifi...
Two-dimensional covalent organic frameworks (2D COFs) are an interesting class of 2D materials since their reticular synthesis allows the tailored design of structures and functionalities. For many of their applications the mechanical stability and performance is an important aspect. Here, we use a computational approach involving a density-functio...
Both ammonia (NH3) and phosphine (PH3) play a significant role in an extensive range of industrial processes, while they are harmful to human health even at very low concentration. So far, a variety of gas sensors have been developed to detect them in an industrial environment aimed to protect the health of workers at their work place. Among variou...
Molecule- and solid-state gears build the elementary constituents of nanoscale mechanical machineries. Recent experimental advances in fabrication technologies in the field have strongly contributed to better delineate the roadmap towards the ultimate goal of engineering molecular-scale mechanical devices. To complement experimental studies, comput...
Two-dimensional Covalent Organic Frameworks (2D COFs) have attracted considerable interest because of their potential for a broad range of applications. Different combinations of the monomeric units can lead to potentially novel materials with varying physico-chemical properties. In this study, we investigate the electronic properties of various 2D...
Both ammonia and phosphine are widely used in industrial processes, and yet they are noxious and exhibit detrimental effects on human health. Despite the remarkable progress on sensors development, there are still some limitations, for instance, the requirement of high operating temperatures, and that most sensors are solely dedicated to individual...
The interest in two‐dimensional conjugated polymers (2D CPs) has increased significantly in recent years. In particular, vinylene‐linked 2D CPs with fully in‐plane sp²‐carbon‐conjugated structures, high thermal and chemical stability, have become the focus of attention. Although the Horner‐Wadsworth‐Emmons (HWE) reaction has been recently demonstra...
We perform molecular dynamics simulations to study the collective rotation of a graphene nanodisk functionalized on its circumference by tert-butylphenyl chemical groups in interaction with a molecule-gear hexa-tert-butylphenylbenzene supported by a Cu(111) surface. The rotational motion can be categorized underdriving, driving and overdriving regi...
Lubricants are widely used in macroscopic mechanical systems to reduce friction and wear. However, on the microscopic scale, it is not clear to what extent lubricants are beneficial. Therefore, in this study, we consider two diamond solid-state gears at the nanoscale immersed in different lubricant molecules and perform classical MD simulations to...
Two-dimensional polymers (2DPs) and their layer-stacked 2D covalent organic frameworks (2D COFs) are classes of structurally defined crystalline polymeric materials with exotic physical and chemical properties. Yet, synthesizing 2DP and 2D COF single crystals via irreversible reactions remains challenging. Here we report the synthesis of charged 2D...
Both NH 3 and PH 3 are widely used in industrial processes, and yet they are noxious and exhibit detrimental effects on human health. 1 A variety of gas sensors have been developed to detect and monitor the NH 3 /PH 3 gas in an industrial environment. 2-4 Despite the remarkable progress of sensors development, there are still some limitations, for...
Lubricants are widely used in macroscopic mechanical systems to reduce friction and wear. However, on the microscopic scale, it is not clear to what extent lubricants are beneficial. Therefore, in this study, we consider two diamond solid-state gears at the nanoscale immersed in different lubricant molecules and perform classical MD simulations to...
Lubricants are widely used in macroscopic mechanical systems to reduce friction and wear. However, on the microscopic scale, it is not clear to what extent lubricants are beneficial. Therefore, in this study, we consider two diamond solid-state gears at the nanoscale immersed in different lubricant molecules and perform classical MD simulations to...
Nanoelectromechanical systems (NEMS) are devices integrating electrical and mechanical functionality on the nanoscale. Because of individual electron tunneling, such systems can show rich self-induced, highly nonlinear dynamics. We show theoretically that rotor shuttles, fundamental NEMS without intrinsic frequencies, are able to rectify an oscilla...
Computerpraktika stellen einen wichtigen Bestandteil vieler Lehrveranstaltungen dar, welche die Grundlagen und Details von computergestützten Methoden vermitteln sollen. In den Materialwissenschaften spielen solche Methoden eine zunehmend wichtige Rolle. Typischerweise setzen die Praktika eine physische Präsenz in den PC Pools voraus, u.a. da eine...
Recently, Graphene has attracted intensive attention in the gas sensing field due to its high electrical conductivity as well as large specific surface areas. Lots of graphene-based gas sensor have been reported with excellent gas sensing performance. However, the sensing element materials for most of the above sensors are actually consisted of red...
Porphyrins, phthalocayanines and their derivatives have found interesting applications in various fields such as molecular electronics, optoelectronics, and sensorics. Common to this class of molecules with a metal-free core is the existence of hydrogen tautomerization reactions. Since the reaction only involves the motion of a pair of hydrogen ato...
A growing body of research aims at solving what is often referred to as the stimulus-percept problem in olfactory perception. Although computational efforts have made it possible to predict perceptual impressions from the physicochemical space of odors, studies with large psychophysical datasets from non-experts remain scarce. Following previous ap...
Nanoelectromechanical systems (NEMS) are devices integrating electrical and mechanical functionality on the nanoscale. Because of individual electron tunneling, such systems can show rich self-induced, highly non-linear dynamics. We show theoretically that rotor shuttles, fundamental NEMS without intrinsic frequencies, are able to rectify an oscill...
Compared to nanoscale friction of translational motion, the mechanisms of rotational friction have received less attention. Such motion becomes an important issue for the miniaturization of mechanical machinery that often involves rotating gears. In this study, molecular-dynamics simulations are performed to explore rotational friction for solid-st...
Two-dimensional Covalent Organic Frameworks (2D COFs) have attracted a lot of interest because of their potential for a broad range of applications. Different combinations of their molecular building blocks can lead to new materials with different physical and chemical properties. In this study, the elasticity of different single-layer tetrabenzopo...
Graphene has attracted extraordinary attention for gas sensing due to its large specific surface area as well as its high charge carrier mobility. Nonetheless, in most cases, graphene derivatives, such as reduced graphene oxide (rGO), were employed as sensing elements instead of pristine graphene. In this contribution, pristine graphene noncovalent...
The miniaturization of gears towards the nanoscale is a formidable task posing a variety of challenges to current fabrication technologies. In context, the understanding, via computer simulations, of the mechanisms mediating the transfer of rotational motion between nanoscale gears can be of great help to guide the experimental designs. Based on at...
Compared to nanoscale friction of translational motion, the mechanisms of rotational friction have received less attention. Such motion becomes an important issue for the miniaturization of mechanical machineries which often involve rotating gears. In this study, molecular dynamics simulations are performed to explore rotational friction for solid-...
The miniaturization of gears towards the nanoscale is a formidable task posing a variety of challenges to current fabrication technologies. In context, the understanding, via computer simulations, of the mechanisms mediating the transfer of rotational motion between nanoscale gears can be of great help to guide the experimental designs. Based on at...
The manipulation and coupling of molecule gears is the first step toward realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular-dynamics simulations. Within a nearly rigid-body approximation, we reduce the dynamics of the gears to the rotational motion around the orientation vect...
Manipulating and coupling molecule gears is the first step towards realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular dynamics simulations. Within a nearly rigid-body approximation we reduce the dynamics of the gears to the rotational motion around the orientation vector. Thi...
Flavin mononucleotide sodium (FMNS) was recently reported as a highly efficient dispersant for the exfoliation of defect-free, few-layer, stabilized aqueous graphene dispersions. Most importantly, FMNS is innocuous and eco-friendly and can facilitate biomedical applications of graphene. Complementing those experimental studies, the influence of FMN...
Manipulating and coupling molecule gears is the first step towards realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular dynamics simulations. Within a nearly rigid-body approximation we reduce the dynamics of the gears to the rotational motion around the orientation vector. Thi...
Flavin mononucleotide sodium (FMNS) was reported as a highly efficient bio-dispersant for the exfoliation of aqueous dispersions of defect-free, few-layer graphene flakes. [1] Most importantly, FMNS is innocuous and environment friendly and can facilitate bio-medical applications of graphene. Although there is some experimental work on graphene exf...
Two iron porphyrin complexes with either mesityl (FeTMP) or thiophene (FeT3ThP) peripheral substituents were attached to basal pyrolytic graphite and Ag electrodes via different immobilization methods. By combining cyclic voltammetry and in-operando surface-enhanced Raman spectroscopy along with MD simulations and DFT calculations, their respective...
A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomistic methodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected a...
In this work, a combined modelling approach for crack propagation in defective graphene is presented. Molecular dynamics (MD) simulations are used to obtain material parameters (Young's modulus and Poisson ratio) and to determine the energy contributions during the crack evolution. The elastic properties are then applied in phase-field continuum si...
Downsizing of devices opens the question of how to tune not only their electronic properties, but also of how to influence ‘mechanical’ degrees of freedom such as translational and rotational motions. Experimentally, this has been meanwhile demonstrated by manipulating individual molecules with e.g. current pulses from a Scanning Tunneling Microsco...
We theoretically investigate the influence of defect-induced long-range deformations in carbon nanotubes on their electronic transport properties. To this end we perform numerical ab-initio calculations using a density-functional-based tight-binding model for various tubes with vacancies. The geometry optimization leads to a change of the atomic po...
Phonons play a major role for the performance of nanoscale devices and, conse- quently, a detailed understanding of phonon dynamics is required. Using an auxiliary-mode approach, which has successfully been applied for the case of electrons, we develop a new method to numerically describe time-dependent phonon transport. This method allows one to g...
Graphene, a single layer of graphite with one atom thickness, has attracted extensive attention due to its extraordinary properties. Especially, owning to the excellent electrical conductivity, ultrahigh ratio of surface area to volume, as well as the extreme sensitivity of its surface atoms to any adsorbed molecules or reaction events, graphene po...