Lorenz Kranabetter, Henrik H. Kristensen, Constant A. Schouder, Henrik Stapelfeldt
Alkali trimers, Ak$_3$, located on the surface of He nanodroplets are triply ionized following multiphoton absorption from an intense femtosecond laser pulse leading to fragmentation into three correlated Ak$^+$ ions. Combining the information from three-fold covariance analysis of the emission direction of the fragment ions and from their kinetic energy distributions $P(E_{text{kin}})$, we find that Na$_3$, K$_3$, and Rb$_3$ have an equilateral triangular structure, corresponding to that of the lowest-lying quartet state $^{4}mathrm{A}_{2}'$, and determine the equilibrium bond distance $R_text{eq}$(Na$_3$) = 4.65 $pm$ 0.15 {AA}, $R_text{eq}$(K$_3$) = 5.03 $pm$ 0.18 {AA}, and $R_text{eq}$(Rb$_3$) = 5.45 $pm$ 0.22 {AA}. For K$_3$ and Rb$_3$ these values agree well with existing theoretical calculations, while for Na$_3$ the value is 0.2-0.3 {AA} larger than the existing theoretical results. The discrepancy is ascribed to a minor internuclear motion of Na$_3$ during the ionization process. Also, we determine the distribution of internuclear distances $P(R)$ under the assumption of fixed bond angles. The results are compared to the square of the internuclear wave function $|Psi(R)|^2$.
{"title":"Structure determination of alkali trimers on helium nanodroplets through laser-induced Coulomb explosion","authors":"Lorenz Kranabetter, Henrik H. Kristensen, Constant A. Schouder, Henrik Stapelfeldt","doi":"arxiv-2402.00587","DOIUrl":"https://doi.org/arxiv-2402.00587","url":null,"abstract":"Alkali trimers, Ak$_3$, located on the surface of He nanodroplets are triply\u0000ionized following multiphoton absorption from an intense femtosecond laser\u0000pulse leading to fragmentation into three correlated Ak$^+$ ions. Combining the\u0000information from three-fold covariance analysis of the emission direction of\u0000the fragment ions and from their kinetic energy distributions\u0000$P(E_{text{kin}})$, we find that Na$_3$, K$_3$, and Rb$_3$ have an equilateral\u0000triangular structure, corresponding to that of the lowest-lying quartet state\u0000$^{4}mathrm{A}_{2}'$, and determine the equilibrium bond distance\u0000$R_text{eq}$(Na$_3$) = 4.65 $pm$ 0.15 {AA}, $R_text{eq}$(K$_3$) = 5.03\u0000$pm$ 0.18 {AA}, and $R_text{eq}$(Rb$_3$) = 5.45 $pm$ 0.22 {AA}. For K$_3$\u0000and Rb$_3$ these values agree well with existing theoretical calculations,\u0000while for Na$_3$ the value is 0.2-0.3 {AA} larger than the existing\u0000theoretical results. The discrepancy is ascribed to a minor internuclear motion\u0000of Na$_3$ during the ionization process. Also, we determine the distribution of\u0000internuclear distances $P(R)$ under the assumption of fixed bond angles. The\u0000results are compared to the square of the internuclear wave function\u0000$|Psi(R)|^2$.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"298 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139665574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reaction processes in muon catalyzed fusion ($mu$CF), $(dtmu)_{J=v=0} to alpha + n + mu + 17.6,{rm MeV}:$ or $ ;(alpha mu)_{nl} + n + 17.6,{rm MeV}$ in the D-T mixture was comprehensively studied by Kamimura, Kino and Yamashita [Phys. Rev. C 107, 034607 (2023)] by solving the $dtmu$-$alpha nmu$ coupled channel (CC) Schr"odinger equation under a boundary condition where the muonic molecule $(dtmu)_{J=v=0}$ was set as the initial state and the outgoing wave was in the $alpha nmu$ channel. We approximate this CC framework and propose a considerably more tractable model using the $T$-matrix method based on the Lippmann-Schwinger equation. Nuclear interactions adopted in the $T$-matrix model are determined by reproducing the cross section of the reaction $d + t to alpha + n + 17.6,{rm MeV}$ at low energies. The cross section of the strong-coupling rearrangement reaction is presented in a simple closed form based on our new model. This $T$-matrix model have reproduced most of the calculated results on the above $mu$CF reaction reported by Kamimura et al. (2023) and is applicable to other $mu$CF systems such as $(ddmu)$, $(ttmu)$, $(dtmu)^*$, $(ddmu)^*$.
μ介子催化聚变（$mu$CF）中的反应过程，$(dtmu)_{J=v=0}到α + n + mu + 17. 6 （µ介子催化核聚变）或 $ （α + mu）_{nl}或 $;(αmu)_{nl} + n + 17.6,{rmMeV}$ in the D-T mixture was comprehensively studied by Kamimura, Kino and Yamashita [Phys.C 107, 034607 (2023)]在一个边界条件下求解了 $dtmu$-$alphanmu$ 耦合通道（CC）薛定谔方程，其中μ介子分子$(dtmu)_{J=v=0}$被设定为初始状态，出射波处于$alpha nmu$ 通道。我们使用基于李普曼-施温格方程的 $T$ 矩阵方法对这一 CC 框架进行了近似，并提出了一个更为简便的模型。T$-矩阵模型中采用的核相互作用是通过再现低能下$d + t to alpha + n + 17.6,{rm MeV}$的横截面来确定的。基于我们的新模型，强偶联重排反应的截面以一种简单封闭的形式呈现出来。这个 $T$ 矩阵模型重现了 Kamimura etal.(2023)所报道的上述 $mu$CF 反应的大部分计算结果，并适用于其他 $mu$CF 系统，如 $(ddmu)$、$(ttmu)$、$(dtmu)^*$、$(ddmu)^*$。
{"title":"Tractable $T$-matix model for reaction processes in muon catalyzed fusion $(dtμ)_{J=v=0} to ; α+ n + μ+ 17.6, {rm MeV} ; mbox{or} ; (αμ)_{nl} + n +17.6 ,{rm MeV}$","authors":"Qian Wu, Masayasu Kamimura","doi":"arxiv-2401.17358","DOIUrl":"https://doi.org/arxiv-2401.17358","url":null,"abstract":"Reaction processes in muon catalyzed fusion ($mu$CF), $(dtmu)_{J=v=0} to\u0000alpha + n + mu + 17.6,{rm MeV}:$ or $ ;(alpha mu)_{nl} + n + 17.6,{rm\u0000MeV}$ in the D-T mixture was comprehensively studied by Kamimura, Kino and\u0000Yamashita [Phys. Rev. C 107, 034607 (2023)] by solving the $dtmu$-$alpha\u0000nmu$ coupled channel (CC) Schr\"odinger equation under a boundary condition\u0000where the muonic molecule $(dtmu)_{J=v=0}$ was set as the initial state and\u0000the outgoing wave was in the $alpha nmu$ channel. We approximate this CC\u0000framework and propose a considerably more tractable model using the $T$-matrix\u0000method based on the Lippmann-Schwinger equation. Nuclear interactions adopted\u0000in the $T$-matrix model are determined by reproducing the cross section of the\u0000reaction $d + t to alpha + n + 17.6,{rm MeV}$ at low energies. The cross\u0000section of the strong-coupling rearrangement reaction is presented in a simple\u0000closed form based on our new model. This $T$-matrix model have reproduced most\u0000of the calculated results on the above $mu$CF reaction reported by Kamimura et\u0000al. (2023) and is applicable to other $mu$CF systems such as $(ddmu)$,\u0000$(ttmu)$, $(dtmu)^*$, $(ddmu)^*$.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"141 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139657530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. De, A. R. Abid, J. D. Asmussen, L. Ben Ltaief, K. Sishodia, A. Ulmer, H. B. Pedersen, S. R. Krishnan, M. Mudrich
Helium nanodroplets ("HNDs") are widely used for forming tailor-made clusters and molecular complexes in a cold, transparent, and weakly-interacting matrix. Characterization of embedded species by mass spectrometry is often complicated by fragmentation and trapping of ions in the HNDs. Here, we systematically study fragment ion mass spectra of HND-aggregated water and oxygen clusters following their ionization by charge transfer ionization ("CTI") and Penning ionization ("PEI"). While the efficiency of PEI of embedded clusters is lower than for CTI by about factor 10, both the mean sizes of detected water clusters and the relative yields of unprotonated cluster ions are significantly larger, making PEI a ``soft ionization'' scheme. However, the tendency of ions to remain bound to HNDs leads to a reduced detection efficiency for large HNDs containing $>10^4$ helium atoms. These results are instrumental for determining optimal conditions for mass spectrometry and photoionization spectroscopy of molecular complexes and clusters aggregated in HNDs.
{"title":"Fragmentation of Water Clusters Formed in Helium Nanodroplets by Charge Transfer and Penning Ionization","authors":"S. De, A. R. Abid, J. D. Asmussen, L. Ben Ltaief, K. Sishodia, A. Ulmer, H. B. Pedersen, S. R. Krishnan, M. Mudrich","doi":"arxiv-2401.06527","DOIUrl":"https://doi.org/arxiv-2401.06527","url":null,"abstract":"Helium nanodroplets (\"HNDs\") are widely used for forming tailor-made clusters\u0000and molecular complexes in a cold, transparent, and weakly-interacting matrix.\u0000Characterization of embedded species by mass spectrometry is often complicated\u0000by fragmentation and trapping of ions in the HNDs. Here, we systematically\u0000study fragment ion mass spectra of HND-aggregated water and oxygen clusters\u0000following their ionization by charge transfer ionization (\"CTI\") and Penning\u0000ionization (\"PEI\"). While the efficiency of PEI of embedded clusters is lower\u0000than for CTI by about factor 10, both the mean sizes of detected water clusters\u0000and the relative yields of unprotonated cluster ions are significantly larger,\u0000making PEI a ``soft ionization'' scheme. However, the tendency of ions to\u0000remain bound to HNDs leads to a reduced detection efficiency for large HNDs\u0000containing $>10^4$ helium atoms. These results are instrumental for determining\u0000optimal conditions for mass spectrometry and photoionization spectroscopy of\u0000molecular complexes and clusters aggregated in HNDs.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139470430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anirban Paul, Ian Carmichael, Dhananjay Nandi, Sylwia Ptasinska, Dipayan Chakraborty
Exploring the molecular fragmentation dynamics induced by low-energy electrons offers compelling insights into the complex interplay between the projectile and target. In this study, we investigate the phenomenon of dissociative electron attachment to ethyl acetate. The recorded yields of various fragment anions within an incident electron energy range of 1 to 13 eV reveal a diverse array of products with six different mass numbers. Examples include (M$-$H)$^-$, CH$_3^-$, C$_2$H$_5$O$^-$, CH$_3$CO$^-$, CH$_2$CHO$^-$, and CH$_3$COO$^-$, formed through the fracture of single bonds. Interestingly, the generation of other fragments, such as HCCO$^-$, suggests a more intricate structural rearrangement of the nuclei, adding a layer of complexity to the observed dissociation dynamics.
探索低能电子诱导的分子碎裂动力学，为了解射弹与目标之间复杂的相互作用提供了令人信服的见解。在本研究中，我们研究了电子附着在乙酸乙酯上的解离现象。在 1 到 13 eV 的入射电子能量范围内，记录到的各种碎片阴离子的产率显示了具有六种不同质量数的多种产物。例如，通过单键断裂形成的 (M$-$H)$^-$、CH$_3^-$、C$_2$H$_5$O$^-$、CH$_3$CO$^-$、CH$_2$CHO$^-$ 和 CH$_3$COO$^-$。有趣的是，其他碎片（如 HCCO$^-$）的产生表明原子核发生了更为复杂的结构重排，从而为所观察到的解离动力学增加了一层复杂性。
{"title":"Structural rearrangements and fragmentation pathways induced by a low-energy electron attachment to ethyl acetate","authors":"Anirban Paul, Ian Carmichael, Dhananjay Nandi, Sylwia Ptasinska, Dipayan Chakraborty","doi":"arxiv-2401.02366","DOIUrl":"https://doi.org/arxiv-2401.02366","url":null,"abstract":"Exploring the molecular fragmentation dynamics induced by low-energy\u0000electrons offers compelling insights into the complex interplay between the\u0000projectile and target. In this study, we investigate the phenomenon of\u0000dissociative electron attachment to ethyl acetate. The recorded yields of\u0000various fragment anions within an incident electron energy range of 1 to 13 eV\u0000reveal a diverse array of products with six different mass numbers. Examples\u0000include (M$-$H)$^-$, CH$_3^-$, C$_2$H$_5$O$^-$, CH$_3$CO$^-$, CH$_2$CHO$^-$,\u0000and CH$_3$COO$^-$, formed through the fracture of single bonds. Interestingly,\u0000the generation of other fragments, such as HCCO$^-$, suggests a more intricate\u0000structural rearrangement of the nuclei, adding a layer of complexity to the\u0000observed dissociation dynamics.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139102872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we theoretically calculate the electron impact partial and total ionization cross sections of R-carvone $(C_{10}H_{14}O)$, 2-butanol $(C_{4}H_{10}O)$, imidazole $(C_3H_4N_2)$ and 2-nitroimidazole $(C_3H_3N_3O_2)$. We have used the Binary Encounter Bethe (BEB) model to obtain the total electron impact ionization cross sections (TICS). The modified BEB method in combination with mass spectrum data of the molecules is used to calculate the PICS of the cationic fragments originating from the parent molecule. Our PICS data for R-carvone and 2-butanol are in good agreement with the experimental data for all the cation fragments along with the TICS data. For imidazole and 2-nitroimidazole, the estimates of the PICS are reported for the first time in the present study. We have found that both the modified BEB method and the mass spectrum dependence method work effectively to estimate PICS if we have the information about the appearance energies and mass spectrum data of the target under investigation.
{"title":"Electron impact partial ionization cross sections: R-Carvone, 2-Butanol, Imidazole, and 2-Nitroimidazole","authors":"Suriyaprasanth S, Rounak Agrawal, Dhanoj Gupta","doi":"arxiv-2312.13001","DOIUrl":"https://doi.org/arxiv-2312.13001","url":null,"abstract":"In this work, we theoretically calculate the electron impact partial and\u0000total ionization cross sections of R-carvone $(C_{10}H_{14}O)$, 2-butanol\u0000$(C_{4}H_{10}O)$, imidazole $(C_3H_4N_2)$ and 2-nitroimidazole\u0000$(C_3H_3N_3O_2)$. We have used the Binary Encounter Bethe (BEB) model to obtain\u0000the total electron impact ionization cross sections (TICS). The modified BEB\u0000method in combination with mass spectrum data of the molecules is used to\u0000calculate the PICS of the cationic fragments originating from the parent\u0000molecule. Our PICS data for R-carvone and 2-butanol are in good agreement with\u0000the experimental data for all the cation fragments along with the TICS data.\u0000For imidazole and 2-nitroimidazole, the estimates of the PICS are reported for\u0000the first time in the present study. We have found that both the modified BEB\u0000method and the mass spectrum dependence method work effectively to estimate\u0000PICS if we have the information about the appearance energies and mass spectrum\u0000data of the target under investigation.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138825843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This chapter provides a comprehensive review of fundamental concepts related to approximate natural orbital functionals (NOFs), emphasizing their significance in quantum chemistry and physics. Focusing on fermions, the discussion excludes considerations of finite temperature and systems with a variable number of particles. The theoretical foundation for approximate NOFs is laid out, with a particular emphasis on functional N-representability. Various two-index reconstructions for the two-particle reduced density matrix (2RDM) are introduced, accompanied by discussions on challenges. The analysis delves deeply into NOFs grounded in electron pairing, specifically focusing on PNOF5, PNOF7, and the Global NOF, a more versatile approach addressing both static and dynamic electron correlation components. The extension of NOFs to multiplets while conserving total spin is presented, and the availability of open-source implementations like DoNOF (http://github.com/DoNOF) and its associated programs is highlighted. A detailed overview of optimization procedures for single-point calculations is provided. Sections on geometry optimization and ab initio molecular dynamics, closely connected to the availability of analytical gradients in NOF theory, are presented. The chapter concludes with the extension of NOFs to both charged and excited states.
{"title":"Advances in Approximate Natural Orbital Functionals: From Historical Perspectives to Contemporary Developments","authors":"Mario Piris","doi":"arxiv-2312.07163","DOIUrl":"https://doi.org/arxiv-2312.07163","url":null,"abstract":"This chapter provides a comprehensive review of fundamental concepts related\u0000to approximate natural orbital functionals (NOFs), emphasizing their\u0000significance in quantum chemistry and physics. Focusing on fermions, the\u0000discussion excludes considerations of finite temperature and systems with a\u0000variable number of particles. The theoretical foundation for approximate NOFs\u0000is laid out, with a particular emphasis on functional N-representability.\u0000Various two-index reconstructions for the two-particle reduced density matrix\u0000(2RDM) are introduced, accompanied by discussions on challenges. The analysis\u0000delves deeply into NOFs grounded in electron pairing, specifically focusing on\u0000PNOF5, PNOF7, and the Global NOF, a more versatile approach addressing both\u0000static and dynamic electron correlation components. The extension of NOFs to\u0000multiplets while conserving total spin is presented, and the availability of\u0000open-source implementations like DoNOF (http://github.com/DoNOF) and its\u0000associated programs is highlighted. A detailed overview of optimization\u0000procedures for single-point calculations is provided. Sections on geometry\u0000optimization and ab initio molecular dynamics, closely connected to the\u0000availability of analytical gradients in NOF theory, are presented. The chapter\u0000concludes with the extension of NOFs to both charged and excited states.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138628888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Arthur-Baidoo, J. R. Danielson, C. M. Surko, J. P. Cassidy, S. K. Gregg, J. Hofierka, B. Cunningham, C. H. Patterson, D. G. Green
Annihilation spectra are presented for aromatic and heterocyclic ring molecules resolved as a function of incident positron energy using a trap-based positron beam. Comparisons with the vibrational mode spectra yield positron-molecule binding energies. Good to excellent agreement is found between the measured binding energies and the predictions of an textit{ab initio} many-body theory that takes proper account of electron-positron correlations including virtual-positronium formation. The calculations elucidate the competition between permanent dipole moments and $pi$ bonds in determining the spatial distribution of the bound-state positron density. The implications of these results and the role of multimode features in annihilation in these molecules, including Fermi resonances, are discussed.
{"title":"Positron annihilation and binding in aromatic and other ring molecules","authors":"E. Arthur-Baidoo, J. R. Danielson, C. M. Surko, J. P. Cassidy, S. K. Gregg, J. Hofierka, B. Cunningham, C. H. Patterson, D. G. Green","doi":"arxiv-2312.02779","DOIUrl":"https://doi.org/arxiv-2312.02779","url":null,"abstract":"Annihilation spectra are presented for aromatic and heterocyclic ring\u0000molecules resolved as a function of incident positron energy using a trap-based\u0000positron beam. Comparisons with the vibrational mode spectra yield\u0000positron-molecule binding energies. Good to excellent agreement is found\u0000between the measured binding energies and the predictions of an textit{ab\u0000initio} many-body theory that takes proper account of electron-positron\u0000correlations including virtual-positronium formation. The calculations\u0000elucidate the competition between permanent dipole moments and $pi$ bonds in\u0000determining the spatial distribution of the bound-state positron density. The\u0000implications of these results and the role of multimode features in\u0000annihilation in these molecules, including Fermi resonances, are discussed.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This note establishes, first of all, the monotonic increase with $N$ of the average $K$-body energy of classical $N$-body ground state configurations with $Ngeq K$ monomers that interact solely through a permutation-symmetric $K$-body potential, for any fixed integer $Kgeq 2$. For the special case $K=2$ this result had previously been proved, and used successfully as a test criterion for optimality of computer-generated lists of putative ground states of $N$-body clusters for various types of pairwise interactions. Second, related monotonicity results are established for $N$-monomer ground state configurations whose monomers interact through additive mixtures of certain types of $k$-meric potentials, $kin{1,...,K}$, with $Kgeq 2$ fixed and $Ngeq K$. All the monotonicity results furnish simple necessary conditions for optimality that any pertinent list of computer-generated putative global minimum energies for $N$-monomer clusters has to satisfy. As an application, databases of $N$-body cluster energies computed with an additive mix of the dimeric Lennard-Jones and trimeric Axilrod--Teller interactions are inspected. We also address how many local minima satisfy the upper bound inferred from the monotonicity conditions, both from a theoretical and from an empirical perspective.
{"title":"On the global minimum of the classical potential energy for clusters bound by many-body forces","authors":"Michael K. -H. Kiessling, David J. Wales","doi":"arxiv-2312.00988","DOIUrl":"https://doi.org/arxiv-2312.00988","url":null,"abstract":"This note establishes, first of all, the monotonic increase with $N$ of the\u0000average $K$-body energy of classical $N$-body ground state configurations with\u0000$Ngeq K$ monomers that interact solely through a permutation-symmetric\u0000$K$-body potential, for any fixed integer $Kgeq 2$. For the special case $K=2$\u0000this result had previously been proved, and used successfully as a test\u0000criterion for optimality of computer-generated lists of putative ground states\u0000of $N$-body clusters for various types of pairwise interactions. Second,\u0000related monotonicity results are established for $N$-monomer ground state\u0000configurations whose monomers interact through additive mixtures of certain\u0000types of $k$-meric potentials, $kin{1,...,K}$, with $Kgeq 2$ fixed and\u0000$Ngeq K$. All the monotonicity results furnish simple necessary conditions for\u0000optimality that any pertinent list of computer-generated putative global\u0000minimum energies for $N$-monomer clusters has to satisfy. As an application,\u0000databases of $N$-body cluster energies computed with an additive mix of the\u0000dimeric Lennard-Jones and trimeric Axilrod--Teller interactions are inspected.\u0000We also address how many local minima satisfy the upper bound inferred from the\u0000monotonicity conditions, both from a theoretical and from an empirical\u0000perspective.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"18 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Interstitial diffusion is a pivotal process that governs the phase stability and irradiation response of materials in non-equilibrium conditions. In this work, we study sluggish and chemically-biased interstitial diffusion in Fe-Ni concentrated solid solution alloys (CSAs) by combining machine learning (ML) and kinetic Monte Carlo (kMC), where ML is used to accurately and efficiently predict the migration energy barriers on-the-fly. The ML-kMC reproduces the diffusivity that was reported by molecular dynamics results at high temperatures. With this powerful tool, we find that the observed sluggish diffusion and the "Ni-Ni-Ni"-biased diffusion in Fe-Ni alloys are ascribed to a unique "Barrier Lock" mechanism, whereas the "Fe-Fe-Fe"-biased diffusion is influenced by a "Component Dominance" mechanism. Inspired by the mentioned mechanisms, a practical AvgS-kMC method is proposed for conveniently and swiftly determining interstitial-mediated diffusivity by only relying on the mean energy barriers of migration patterns. Combining the AvgS-kMC with the differential evolutionary algorithm, an inverse design strategy for optimizing sluggish diffusion properties is applied to emphasize the crucial role of favorable migration patterns.
{"title":"Sluggish and Chemically-Biased Interstitial Diffusion in Concentrated Solid Solution Alloys: Mechanisms and Methods","authors":"Biao Xu, Haijun Fu, Shasha Huang, Shihua Ma, Yaoxu Xiong, Jun Zhang, Xuepeng Xiang, Wenyu Lu, Ji-Jung Kai, Shijun Zhao","doi":"arxiv-2311.16727","DOIUrl":"https://doi.org/arxiv-2311.16727","url":null,"abstract":"Interstitial diffusion is a pivotal process that governs the phase stability\u0000and irradiation response of materials in non-equilibrium conditions. In this\u0000work, we study sluggish and chemically-biased interstitial diffusion in Fe-Ni\u0000concentrated solid solution alloys (CSAs) by combining machine learning (ML)\u0000and kinetic Monte Carlo (kMC), where ML is used to accurately and efficiently\u0000predict the migration energy barriers on-the-fly. The ML-kMC reproduces the\u0000diffusivity that was reported by molecular dynamics results at high\u0000temperatures. With this powerful tool, we find that the observed sluggish\u0000diffusion and the \"Ni-Ni-Ni\"-biased diffusion in Fe-Ni alloys are ascribed to a\u0000unique \"Barrier Lock\" mechanism, whereas the \"Fe-Fe-Fe\"-biased diffusion is\u0000influenced by a \"Component Dominance\" mechanism. Inspired by the mentioned\u0000mechanisms, a practical AvgS-kMC method is proposed for conveniently and\u0000swiftly determining interstitial-mediated diffusivity by only relying on the\u0000mean energy barriers of migration patterns. Combining the AvgS-kMC with the\u0000differential evolutionary algorithm, an inverse design strategy for optimizing\u0000sluggish diffusion properties is applied to emphasize the crucial role of\u0000favorable migration patterns.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The emergence of the first bilayer B48, which has been both theoretically predicted and experimentally observed, as well as the recent experimental synthesis of bilayer borophene on Ag and Cu, has generated tremendous curiosity in the bilayer structure of boron clusters. However, the connection between the bilayer cluster and the bilayer borophene remains unknown. By combining a genetic algorithm and density functional theory calculations, a global search for the low-energy structures of B63 clusters was conducted, revealing that the Cs bilayer structure with three interlayer B-B bonds was the most stable bilayer structure. This structure was further examined in terms of its structural stability, chemical bonding, and aromaticity. Interestingly, the interlayer bonds exhibited electronegativity and robust aromaticity. Furthermore, the double aromaticity stemmed from diatropic currents originating from virtual translational transitions at both the sigma and pi electrons. This new boron bilayer is anticipated to enrich the concept of double aromaticity and serve as a valuable precursor for bilayer borophene.
{"title":"B63: the most stable bilayer structure with dual aromaticity","authors":"Jinhuang Chen, Rui Liao, Linwei Sai, Xue Wu, Jijun Zhao","doi":"arxiv-2311.13772","DOIUrl":"https://doi.org/arxiv-2311.13772","url":null,"abstract":"The emergence of the first bilayer B48, which has been both theoretically\u0000predicted and experimentally observed, as well as the recent experimental\u0000synthesis of bilayer borophene on Ag and Cu, has generated tremendous curiosity\u0000in the bilayer structure of boron clusters. However, the connection between the\u0000bilayer cluster and the bilayer borophene remains unknown. By combining a\u0000genetic algorithm and density functional theory calculations, a global search\u0000for the low-energy structures of B63 clusters was conducted, revealing that the\u0000Cs bilayer structure with three interlayer B-B bonds was the most stable\u0000bilayer structure. This structure was further examined in terms of its\u0000structural stability, chemical bonding, and aromaticity. Interestingly, the\u0000interlayer bonds exhibited electronegativity and robust aromaticity.\u0000Furthermore, the double aromaticity stemmed from diatropic currents originating\u0000from virtual translational transitions at both the sigma and pi electrons. This\u0000new boron bilayer is anticipated to enrich the concept of double aromaticity\u0000and serve as a valuable precursor for bilayer borophene.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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