Automated intelligent design of modified uni-traveling carrier photodectors.

This paper introduces an automatic intelligent design method for the modified uni-traveling carrier photodetector (MUTC-PD). The conventional photodetector design process often relies on the numerical solution of complex nonlinear partial differential equations to simulate and optimize device performance, which is not only computationally intensive but also inefficient. To overcome this challenge, we apply the charge control principle to calculate the photodetector bandwidth, which improves the computational speed by a factor of approximately 1800 compared to the numerical solution of nonlinear partial differential equations. To further optimize the structure of the photodetector, we incorporate the Velocity Varying Climbing Particle Swarm Optimization (VVCPSO) algorithm. This is an improved algorithm based on the traditional particle swarm algorithm, which is able to quickly find the optimal solution in a complex parameter space. By applying the VVCPSO algorithm, we successfully fine-tuned the photodetector structure and obtained structural parameters with optimal performance. Our thorough verification process confirms that the proposed method is consistent with the results of ATLAS simulation software. Automated design has resulted in a high-performance MUTC-PD with a responsivity of 0.52A/W and a bandwidth of 60 GHz (@-3 V) at a mesa diameter of 16µm. Compared to the pre-optimized device, the bandwidth is increased to three times the original. By reducing the mesa diameter to 4µm, the bandwidth can be further increased to 82 GHz (@-3 V). The proposed method's calculation speed is fast enough, enabling extensive parameter studies to optimize device performance.

Multi-omics characterization of a scoring system to quantify hypoxia patterns in patients with head and neck squamous cell carcinoma.

BACKGROUND: The 5-year survival rate of patients with head and neck squamous cell carcinoma (HNSCC) remains < 50%. Hypoxia patterns are a hallmark of HNSCC that are associated with its occurrence and progression. However, the precise role of hypoxia during HNSCC, such as the relationship between hypoxia, tumor immune landscape and cell communication orchestration remains largely unknown. The current study integrated data from bulk and single-cell RNA sequencing analyses to define the relationship between hypoxia and HNSCC. METHODS: A scoring system named the hypoxia score (HS) was constructed based on hypoxia-related genes (HRGs) expression. The predictive value of HS response for patient outcomes and different treatments was evaluated. Single-cell datasets and cell communication were utilized to rule out cell populations which hypoxia targeted on. RESULTS: The survival outcomes, immune/Estimate scores, responses to targeted inhibitors, and chemotherapeutic, and immunotherapy responses were distinct between a high HS group and a low HS group (all P < 0.05). Single-cell datasets showed different distributions of HS in immune cell populations (P < 0.05). Furthermore, HLA-DPA1/CD4 axis was identified as a unique interaction between CD4 + T Conv and pDC cells. CONCLUSIONS: Altogether, the quantification for hypoxia patterns is a potential biomarker for prognosis, individualized chemotherapeutic and immunotherapy strategies. The portrait of cell communication characteristics over the HNSCC ecosystem enhances the understanding of hypoxia patterns in HNSCC.

Learning Curve of Robot-Assisted Lymph Node Dissection of the Left Recurrent Laryngeal Nerve: A Retrospective Study of 417 Patients.

OBJECTIVE: Left recurrent laryngeal nerve (no.106recL) lymph node dissection is a challenging procedure, and robotic-assisted minimally invasive esophagectomy (RAMIE) may have some advantages. This study aimed to determine the learning curve of no.106recL lymph node dissection. METHODS: The data of 417 patients who underwent McKeown RAMIE between June 2017 and June 2022 were retrospectively analyzed. The lymph node harvest of no.106recL was used to determine the learning curve, and the cumulative sum (CUSUM) method was employed to obtain the inflection point. RESULTS: A total of 404 patients (404/417, 96.9%) underwent robotic surgery. Based on the number of no.106recL lymph nodes harvested, the CUSUM learning curve was mapped and divided into three phases: phase I (1‒75 cases), phase II (76‒240 cases), and phase III (241‒404 cases). The median (IQR) number of no.106recL lymph node harvests were 1 (4), 3 (6,) and 4 (4) in each phase (p < 0.001). The lymph node dissection rate gradually increased from 62.7% in phase I to 82.9% in phase III (p = 0.001). The total and thoracic lymph node harvest gradually increased (p < 0.001), whereas operation time (p = 0.001) and blood loss gradually decreased (p < 0.001). Moreover, the incidence of total complication (p = 0.020) and recurrent laryngeal nerve injury (p = 0.001) significantly decreased, and the postoperative hospital stay gradually shortened (p < 0.001). CONCLUSION: Robotic no.106recL lymph node dissection has some advantages for patients with esophageal cancer. In this study, perioperative and clinical outcomes were significantly improved over the learning curve. However, further prospective studies are required to confirm our results.

Simulation and design of a high-speed and high-power modified uni-traveling carrier photodiode based on the electric field distribution in the depletion region.

A modified uni-traveling carrier photodiode with an electric field control layer is proposed to achieve high-speed and high-power performance at a lower bias voltage. By inserting the 10 nm p-type InGaAs electric field control layer between the intrinsic absorption layer and space layer, the electric field distribution in the depleted absorption layer and depleted non-absorption layer can be changed. It is beneficial for reducing power consumption and heat generation, meanwhile suppressing the space-charge effect. Compared with the original structure without the electric field control layer, the 3 dB bandwidth of the 20 µm diameter novel structure, to the best of our knowledge, is improved by 27.1% to 37.5 GHz with a reverse bias of 2 V, and the RF output power reaches 23.9 dBm at 30 GHz. In addition, under 8 V bias voltage, the bandwidth reaches 47.3 GHz.

Berberine alleviates intestinal barrier dysfunction in glucolipid metabolism disorder hamsters by modulating gut microbiota and gut-microbiota-related tryptophan metabolites.

BACKGROUND: Barberry plants can be considered as useful additives and functional compounds in various industries, especially in the food industry. Berberine (BBR), the most important functional compound in the barberry roots, has recently been used to treat obesity, diabetes, and atherosclerosis. Gut microbiota and the intestinal barrier play an important role in the development of glucolipid metabolism disorders (GLMDs). However, the association of gut microbiota metabolism disorder and the intestinal barrier dysfunction effect of BBR in GLMDs remains elusive. RESULTS: The results showed that administration of BBR could increase the number of colonic glands and goblet cell mucus secretion, improve the intestinal barrier function, and reduce the serum glycolipid level in GLMD hamsters. Interestingly, BBR was metabolized into 12 metabolites by gut microbiota, and the main metabolic pathways were oxidation, demethylation, and hydrogenation. In addition, BBR significantly improved the species diversity and uniformity of gut microbiota and promoted the proliferation of beneficial microbiota. Furthermore, the levels of tryptophan metabolites, such as indole, indole-3-acetamide, indole-3-acetaldehyde, indole-3-pyruvic acid, and indole-3-acetic acid were significantly altered by BBR. Both the intestinal tight junction proteins and intestinal immune factors were altered by BBR. CONCLUSION: BBR could alleviate intestinal barrier dysfunction of GLMDs by modulating gut microbiota and gut-microbiota-related tryptophan metabolites, which may be one of the pharmacological mechanisms for the treatment of GLMDs. © 2022 Society of Chemical Industry.

Inverse design of sub-wavelength convergent grating based on the "stepped particle swarm algorithm".

In this Letter, a novel "stepped particle swarm optimization" (SPSO) based on field intensity adjustment is proposed. After that, we used this algorithm to design a sub-wavelength converging grating that could be integrated with the detector on the back. Firstly, the advantages of reverse design in the process of two-dimensional or multi-element grating pattern design were summarized by comparing the theory of forward and reverse design. Then, the common "particle swarm optimization" (PSO) and our proposal were compared in the reverse design process; we found that the field strength at the focal point obtained by the improved algorithm was approximately twice of the conventional PSO, and the SPSO had higher computational efficiency and better global convergence. The value of the SPSO had been steadily enlarged, which significantly improved the performance of the sub-wavelength convergent grating. Finally, the property of the sub-wavelength converging grating was simulated, and we found that the grating could achieve good convergence in the focal length range of 100-150 µm, and had a strong ability to compensate for the position deviation of the incident light. In actual optical communications, this sub-wavelength converging grating will play an important role in alleviating the bandwidth and quantum efficiency, improving the performance of the detectors.

Systematic analysis of the function and prognostic value of RNA binding protein in head and neck squamous cell carcinoma.

OBJECTIVE: Dysregulation of RNA binding proteins (RBPs) plays an important role in controlling processes in cancer development. However, the function of RBPs has not been thoroughly and systematically documented in head and neck cancer. We aim to explore the role of RPB in the pathogenesis of HNSC. METHODS: We obtained HNSC gene expression data and corresponding clinical information from The Cancer Genome Atlas (TCGA) and the GEO databases, and identified aberrantly expressed RBPs between tumors and normal tissues. Meanwhile, we performed a series of bioinformatics to explore the function and prognostic value of these RBPs. RESULTS: A total of 249 abnormally expressed RBPs were identified, including 101 downregulated RBPs and 148 upregulated RBPs. Using least absolute shrinkage and selection operator (LASSO) and univariate Cox regression analysis, the 15 RPBs were identified as hub genes. With the 15 RPBS, the prognostic prediction model was constructed. Further analysis showed that the high-risk score of the patients expressed a better survival outcome. The prediction model was validated in another HNSC dataset, and similar findings were observed. CONCLUSIONS: Our results provide novel insights into the pathogenesis of HNSC. The fifteen RBP gene signature exhibited the predictive value of moderate HNSC prognosis, and have potential application value in clinical decision-making and individualized treatment.

Compound glycyrrhiza oral solution alleviates oxidative stress and inflammation by regulating SRC/MAPK pathway in chronic obstructive pulmonary disease.

OBJECTIVES: Patients with chronic obstructive pulmonary disease (COPD) suffer from persistent cough and breathlessness, which can be ameliorated by the Chinese herbal medicine glycyrrhiza. Furthermore, the SRC/MAPK pathway is activated in the process of oxidative stress and inflammation, which afflict COPD progression. Thus, this research aimed at dissecting the mechanism of compound glycyrrhiza oral solution (CGOS) relieving oxidative stress and inflammation in COPD via the SRC/MAPK pathway. METHODS: After a COPD rat model was established using lipopolysaccharide and cigarette smoke, rats underwent intragastric administration with CGOS and intratracheal injection with LV-NC and LV-SRC lentivirus into lungs. Then, pulmonary function-related indexes were evaluated, followed by analyses of arterial blood and inflammatory cell number in prepared bronchoalveolar lavage fluids. Meanwhile, the contents of oxidative stress-related indicators (malondialdehyde, 3NT, 8-Isoprostane, glutathione, NO, and SOD) in pulmonary tissues were measured, along with RT-qPCR and ELISA detection of the expression of inflammatory factors (TNF-α, IL-1ß, IL-4, and IL-10). Moreover, western blot assay was utilized to assess p-SRC/SRC and p-p38/p38 ratios in pulmonary tissues. RESULTS: CGOS treatment enhanced PaO2 and reduced PaCO2 in COPD rats, accompanied by declines in the number of total cells, neutrophils, and macrophages. CGOS improved pulmonary function, decreased malondialdehyde, 3NT, 8-Isoprostane, TNF-α, and IL-1ß levels, and increased GSH, NO, IL-4, and IL-10 levels and SOD activity. Mechanistically, CGOS suppressed the SRC/MAPK pathway, and SRC overexpression reversed the alleviating function of CGOS in COPD rats. CONCLUSIONS: In conclusion, CGOS might alleviate oxidative stress and inflammation in COPD rats by inhibiting the SRC/MAPK pathway.

A nomogram to predict lymph node metastasis risk for early esophageal squamous cell carcinoma.

BACKGROUND: A nomogram was developed to predict lymph node metastasis (LNM) for patients with early-stage esophageal squamous cell carcinoma (ESCC). METHODS: We used the clinical data of ESCC patients with pathological T1 stage disease who underwent surgery from January 2011 to June 2018 to develop a nomogram model. Multivariable logistic regression was used to confirm the risk factors for variable selection. The risk of LNM was stratified based on the nomogram model. The nomogram was validated by an independent cohort which included early ESCC patients underwent esophagectomy between July 2018 and December 2019. RESULTS: Of the 223 patients, 36 (16.1%) patients had LNM. The following three variables were confirmed as LNM risk factors and were included in the nomogram model: tumor differentiation (odds ratio [OR] = 3.776, 95% confidence interval [CI] 1.515-9.360, p = 0.004), depth of tumor invasion (OR = 3.124, 95% CI 1.146-8.511, p = 0.026), and tumor size (OR = 2.420, 95% CI 1.070-5.473, p = 0.034). The C-index was 0.810 (95% CI 0.742-0.895) in the derivation cohort (223 patients) and 0.830 (95% CI 0.763-0.902) in the validation cohort (80 patients). CONCLUSIONS: A validated nomogram can predict the risk of LNM via risk stratification. It could be used to assist in the decision-making process to determine which patients should undergo esophagectomy and for which patients with a low risk of LNM, curative endoscopic resection would be sufficient.

Lymph node dissection around left recurrent laryngeal nerve: robot-assisted vs. video-assisted McKeown esophagectomy for esophageal squamous cell carcinoma.

OBJECTIVE: This study investigated the advantages of robot-assisted McKeown esophagectomy (RAME) for extensive superior mediastinal lymph node dissection (LND) versus video-assisted McKeown esophagectomy (VAME). METHODS: The cases of 184 consecutive esophageal squamous cell carcinoma (ESCC) patients who underwent minimally invasive McKeown esophagectomy (109 with RAME, 75 with VAME) performed by a single surgical group between June 2017 and December 2019 were retrospectively reviewed. RESULTS: Overall, 59.8% (110/181) patients (70 treated with RAME, 40 treated with VAME; 64.2% vs. 53.3%, respectively, p = 0.139) underwent complete LND around the left recurrent laryngeal nerve (RLN) by pathological assessment. Cumulative sum plots showed increased numbers of LND around the left RLN (3.6 ± 2.0 vs. 5.4 ± 2.7, p = 0.008) and a decreased incidence of recurrent nerve injury (27.9% vs. 7.4%, p = 0.037) after RAME learning curve. Despite similar overall LND results (30.6 ± 10.2 vs. 28.1 ± 10.2, p > 0.05), RAME yielded more LND (5.4 ± 2.7 vs. 4.4 ± 2.2, p = 0.016) and a greater proportion of lymph node metastases (37.0% vs. 7.5%) around the left RLN but induced a lower proportion of recurrent nerve injuries (7.4% vs. 22.5%, p = 0.178) compared with VAME. Further analysis revealed that the complete LND around the left RLN was associated with recurrent nerve injury in the RAME (20.0% vs. 5.1%, p = 0.035) and VAME (22.5% vs. 5.7%, p = 0.041) groups but did not affect other clinical outcomes including surgical duration, intraoperative blood loss, postoperative intensive care unit stay, hospital stay, and other complications. CONCLUSIONS: For patients with ESCC, RAME has great advantages in LND around the left RLN and recurrent nerve protection after learning curve of robotic esophagectomy.

Systematic analysis of ACE2 and TMPRSS2 expression in salivary glands reveals underlying transmission mechanism caused by SARS-CoV-2.

Coronavirus disease 2019 (COVID-19) is a global pandemic that has caused severe health threats and fatalities in almost all communities. Studies have detected severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in saliva with a viral load that lasts for a long period. However, researchers are yet to establish whether SARS-CoV-2 can directly enter the salivary glands. Therefore, this study aimed to assess the presence of angiotensin-converting enzyme 2 (ACE2)/transmembrane serine proteases 2 (TMPRSS2) expression in salivary glands using publicly available databases. The distribution of ACE2 and TMPRSSs family in salivary gland tissue and other tissues was analyzed. The Genotype-Tissue Expression dataset was employed to explore the ACE2 and TMPRSS2 expression in various body organs and salivary glands in a healthy population. The single-cell sequencing data for salivary gland samples (including submandibular salivary gland and parotid gland) from mice were collected and analyzed. The components and proportions of salivary gland cells expressing the key protease TMPRSSs family were analyzed. Transcriptome data analysis showed that ACE2 and TMPRSS2 were expressed in salivary glands. The expression levels of ACE2 and TMPRSS2 were marginal without significant differences in different age groups or between men and women. Single-cell RNA sequence analysis indicated that TMPRSS2 was mainly expressed in salivary gland epithelial cells. We speculate that SARS-CoV-2 may be entered in salivary glands.

Influence of Induction Therapy on Robot-Assisted McKeown Esophagectomy for Esophageal Squamous Cell Carcinoma.

BACKGROUND: The present study was to investigate the influence of induction therapy on robot-assisted McKeown esophagectomy (RAME) with radical superior mediastinal lymph node dissection for esophageal squamous cell carcinoma in a high-volume cancer center. METHODS: A consecutive patient cohort who underwent RAME from January 2017 to May 2019 were reviewed. The perioperative outcomes of patients with induction therapy were compared with those who had surgery alone. RESULTS: In total, 118 patients underwent RAME during the study period. The average age was 59.1 ± 7.5 years, including 100 male and 18 female patients. Thirty patients (25.4%) had induction therapy, and 88 patients did not receive induction therapy. The average age of the patients treated with induction therapy was younger than those received surgery alone (56.8 ± 6.1 vs. 59.5 ± 7.6 years, p = 0.039). There were no statistically significant differences in the mean operative time and estimated blood loss between both groups. Complications occurred in 46 (39.0%) patients. There were no statistically significant differences in the rates of any complications between both groups (p = 0.951). There were no deaths in either group. The hospital stay was prolonged in patients with induction therapy than those in the surgery-alone group (20.8 ± 8.9 vs. 16.8 ± 6.0, p = 0.048). There was no statistically significant difference in the average number of dissected lymph nodes in total and both recurrent laryngeal nerve stations between both groups. CONCLUSION: For patients with esophageal squamous cell carcinoma, induction therapy has no influence on RAME with radical superior mediastinal lymph node dissection.

TERT-mediated and ATRX-mediated Telomere Maintenance and Neuroblastoma.

Neuroblastomas (NB) are one of the most common extracranial solid tumors in children, and they frequently display high heterogeneity in the disease course. With ongoing research, more information regarding the genetic etiology and molecular mechanisms underlying these contrasting phenotypes is being uncovered. The proto-oncogene MYCN is amplified in approximately 20% of NB cases and is considered a indicator of poor prognosis and an indicator of high-risk NB. The poor prognosis of high risk NB is incompletely explained by MYCN amplification. Recently, massive parallel sequencing studies reported several relatively common gene alterations, such as ATRX mutation and TERT rearrangement that are involved in telomere maintenance through telomerase activity and alternative lengthening of telomeres. Thus, these are important for understanding the etiology and molecular pathogenesis of NB, and hence, for identifying diagnostic and treatment markers. Development of telomerase inhibitors and identification of alternative lengthening of telomeres related targets will contribute to the individualized treatment for high-risk NB. In this mini-review, we will discuss the research progress of TERT-mediated and ATRX-mediated telomere maintenance and NB, especially high-risk tumors.

Valence and charge-transfer optical properties for some SinCm (m, n ≤ 12) clusters: Comparing TD-DFT, complete-basis-limit EOMCC, and benchmarks from spectroscopy.

Accurate optical characterization of the closo-Si12C12 molecule is important to guide experimental efforts toward the synthesis of nano-wires, cyclic nano-arrays, and related array structures, which are anticipated to be robust and efficient exciton materials for opto-electronic devices. Working toward calibrated methods for the description of closo-Si12C12 oligomers, various electronic structure approaches are evaluated for their ability to reproduce measured optical transitions of the SiC2, Si2Cn (n = 1-3), and Si3Cn (n = 1, 2) clusters reported earlier by Steglich and Maier [Astrophys. J. 801, 119 (2015)]. Complete-basis-limit equation-of-motion coupled-cluster (EOMCC) results are presented and a comparison is made between perturbative and renormalized non-iterative triples corrections. The effect of adding a renormalized correction for quadruples is also tested. Benchmark test sets derived from both measurement and high-level EOMCC calculations are then used to evaluate the performance of a variety of density functionals within the time-dependent density functional theory (TD-DFT) framework. The best-performing functionals are subsequently applied to predict valence TD-DFT excitation energies for the lowest-energy isomers of SinC and Sin-1C7-n (n = 4-6). TD-DFT approaches are then applied to the SinCn (n = 4-12) clusters and unique spectroscopic signatures of closo-Si12C12 are discussed. Finally, various long-range corrected density functionals, including those from the CAM-QTP family, are applied to a charge-transfer excitation in a cyclic (Si4C4)4 oligomer. Approaches for gauging the extent of charge-transfer character are also tested and EOMCC results are used to benchmark functionals and make recommendations.

High-power symmetric-connected uni-traveling-carrier photodiode array integrated with sub-wavelength gratings based beam-splitter.

We present a two-element back-illuminated symmetric-connected uni-traveling-carrier photodiode array (SC-PDA) integrated with sub-wavelength-gratings based beam-splitter (SWGs-BS) for high power optoelectronic applications. The SC-PDA with SWGs-BS, a top-illuminated SC-PDA and a single PD were fabricated and tested. The proposed SC-PDA with SWGs-BS demonstrates a 3dB bandwidth of 23.8GHz@60mA, a saturation current of 87.9mA@12GHz and a maximum output RF power of ~16dBm@12GHz. Compared to the top-illuminated SC-PDA and the single PD, the proposed SC-PDA with SWGs-BS achieved high-power handling capability at low coupling complexity and requires no phase-matching techniques in the system.

The closo-Si12C12 molecule from cluster to crystal: Effects of hydrogenation and oligomerization on excited states.

Excited state properties of chain and cyclic oligomers of closo-Si12C12 moieties are calculated using time-dependent density functional theory methods. Ultraviolet, visible, and near-infrared photo-absorption properties are described for oligomers that form by linking closo-Si12C12 monomer moieties through Si-Si bonds. Natural transition orbitals for electron and hole states of stationary-state excitons in oligomers were compared to understand how exciton states are influenced by oligomer structure. Depending on the structure, some prominent excited states have large electron-hole charge separation while others do not; some exhibit exciton delocalization while others do not. With increasing oligomer length, the character of the transition between silicon and carbon regions tends to be maintained. And the extent of exciton delocalization and charge separation for an excitation is strongly influenced by the number and types of Si-Si links between oligomer units. We find that cyclic quadramers have spectroscopy properties akin to those of J-aggregates, including the tendency to collapse oligomer excitation transition energies into a narrow single peak. Hydrogenation influences some excited state distributions and energies. Phase behaviors reveal electron state or hole state equivalence in certain molecules that are differently hydrogenated, illustrating the potential for near-resonant exciton transfer between adjacent donor and acceptor species.

High Body Mass Index Worsens Survival in Patients with Esophageal Squamous Cell Carcinoma after Esophagectomy.

AIMS: To investigate the prognostic significance of body mass index (BMI) on the survival of patients with esophageal squamous cell carcinoma (ESCC) after esophagectomy. METHODS: Between 2005 and 2008, 291 patients with ESCC who met the inclusion criteria were included in the study. The BMI cut-off values were as follows: 18.5-23 kg/m2 for normal weight; 23-27.5 kg/m2 for overweight; and ≥27.5 kg/m2 for those with obesity. Univariate and multivariate analyses were performed to identify prognostic factors for long-term survival. RESULTS: Patients were divided into 3 groups: normal weight (n = 138), overweight (n = 103), and obese (n = 50). The median survival time was 56 months. The 5-year overall survival (OS) rates were 40.8, 44.7, and 20.8% for normal weight, overweight, and obese patients respectively (p < 0.05). Multivariate analysis identified BMI as an independent prognostic factor for OS (p < 0.05). For 179 patients without lymph node metastasis, the 5-year OS rates were 46.5, 50.7, and 27.0% for normal weight, overweight, and obese patients respectively (p < 0.05). CONCLUSIONS: A BMI ≥27.5 kg/m2 has a distinctly adverse impact on the long-term survival of ESCC patients after esophagectomy. High BMI is a potential predictor of worse prognosis in ESCC patients, particularly in patients without lymph node metastasis.

The closo-Si12C12 molecule from cluster to crystal: A theoretical prediction.

The structure of closo-Si12C12 is unique among stable SinCm isomers (n, m > 4) because of its high symmetry, π-π stacking of C6 rings and unsaturated silicon atoms at symmetrical peripheral positions. Dimerization potential surfaces reveal various dimerization reactions that form between two closo-Si12C12 molecules through Si-Si bonds at unsaturated Si atoms. As a result the closo-Si12C12 molecule is capable of polymerization to form stable 1D polymer chains, 2D crystal layers, and 3D crystals. 2D crystal structures formed by side-side polymerization satisfy eight Si valences on each monomer without large distortion of the monomer structure. 3D crystals are formed by stacking 2D structures in the Z direction, preserving registry of C6 rings in monomer moiety.

Predictive coupled-cluster isomer orderings for some SinCm (m, n ≤ 12) clusters: A pragmatic comparison between DFT and complete basis limit coupled-cluster benchmarks.

The accurate determination of the preferred Si12C12 isomer is important to guide experimental efforts directed towards synthesizing SiC nano-wires and related polymer structures which are anticipated to be highly efficient exciton materials for the opto-electronic devices. In order to definitively identify preferred isomeric structures for silicon carbon nano-clusters, highly accurate geometries, energies, and harmonic zero point energies have been computed using coupled-cluster theory with systematic extrapolation to the complete basis limit for set of silicon carbon clusters ranging in size from SiC3 to Si12C12. It is found that post-MBPT(2) correlation energy plays a significant role in obtaining converged relative isomer energies, suggesting that predictions using low rung density functional methods will not have adequate accuracy. Utilizing the best composite coupled-cluster energy that is still computationally feasible, entailing a 3-4 SCF and coupled-cluster theory with singles and doubles extrapolation with triple-ζ (T) correlation, the closo Si12C12 isomer is identified to be the preferred isomer in the support of previous calculations [X. F. Duan and L. W. Burggraf, J. Chem. Phys. 142, 034303 (2015)]. Additionally we have investigated more pragmatic approaches to obtaining accurate silicon carbide isomer energies, including the use of frozen natural orbital coupled-cluster theory and several rungs of standard and double-hybrid density functional theory. Frozen natural orbitals as a way to compute post-MBPT(2) correlation energy are found to be an excellent balance between efficiency and accuracy.