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• Increased number of informal caregivers assist ailing older adults. • Evidence on compassion fatigue among family caregivers remains limited. • Currently, overall compassion fatigue and satisfaction levels were moderate. • There is a potential risk of compassion fatigue for family caregivers. • Findings can be used to develop programs that will mitigate compassion fatigue. Family caregivers play an increasingly important role in providing care services, especially for the aging population. Currently, evidence on compassion fatigue among family caregivers remains limited. Our study aims to assess the levels and related factors of compassion fatigue and compassion satisfaction in family caregivers. We searched nine electronic databases for published observational studies up to 7 October 2021. In our studies, the pooled mean scores of compassion fatigue and compassion satisfaction were 42.35 (95% CI: 28.45–56.24) and 36.41 (95% CI: 33.63–39.19), respectively. We considered background, role-related, and social psychological variables to influence the risk of compassion fatigue and compassion satisfaction. Current data suggest that overall compassion fatigue and compassion satisfaction levels were moderate, thus highlighting the potential risk of compassion fatigue for family caregivers. In the future, these findings can be used to develop programs that will mitigate compassion fatigue and improve compassion satisfaction in family caregivers. [ABSTRACT FROM AUTHOR]

This meta-analysis aims to estimate the global prevalence of bullying among nursing students during clinical practice and identify associated factors. Systematic review and meta-analysis. We conducted a comprehensive literature search across ten databases (PubMed, Cochrane, Web of Science, Embase, CINAHL, PsycINFO, Scopus, Chinese Biomedical, China National Knowledge Internet, and WANFANG) from their inception to January 3, 2023. Two researchers independently screened potentially eligible studies, extracted data, and assessed study quality. Data were analyzed using random-effects or fixed-effects models. Subgroup analyses and meta-regression explored the influence of participant and study characteristics on bullying prevalence. Publication bias and sensitivity analyses were also performed. We included 28 studies (N = 9511) from 13 countries on five continents. The pooled estimate of bullying prevalence among nursing students during clinical practice was 65.60 % (95 % CI 55. 75 to 74.27), with no evidence of publication bias (t = 1.51, p -value = 0.14). Subgroup and moderator analyses highlighted the impact of country, continent, publication year, and assessment tool on bullying prevalence. Nursing students face a high prevalence of bullying during clinical practice. Addressing this issue in nursing education requires prioritizing associated factors, fostering a culture of safety, providing effective training, and promoting individual resilience. These actions can prevent and mitigate bullying, creating a supportive and empowering learning environment for future nurses. • Nursing students often face high bullying rates during clinical training. • Study reveals country, continent, publication year, and assessment tool's impact on bullying. • Findings inform strategies to prevent and address bullying, fostering supportive nursing education. [ABSTRACT FROM AUTHOR]

With developing nursing ethics education, the traditional methods of teaching could not meet the learning needs of undergraduates. Improving ethical decision-making to undergraduates is necessary toward promoting nursing ethics. The aim of study is to compare the effect of inquiry-oriented teaching and lecture-based approach on nursing ethics education for undergraduates. A quasi-experimental study was conducted for undergraduate nursing students. Two nursing schools participated in the study in mainland China. A total of 97 undergraduate nursing students participated in the study. The study adopted a quasi-experimental design. The inquiry-oriented teaching group was significantly higher on average scoring than the lecture-based group after intervention in 2 aspects including: professional relationship (P = 0.015) and ethical decision making (P = 0.021). Contrarily, this study also showed that in the lecture-based group the score of foundational theories of nursing ethics was higher than Inquiry-oriented group (P = 0.038). A statistically significant difference was not found between the two groups in 3 scenarios: ethics related to nursing practice, ethics related to nursing research and necessity of learning nursing ethics. Combination of inquiry-oriented teaching and lecture-based approach is suggested as part of design for curriculum of nursing ethics education. [ABSTRACT FROM AUTHOR]

Highlights • TGF-β1 up-regulated LOXL1 expression in LX2 cells. • Knockdown of LOXL1 inhibited TGF-β1-induced proliferation of LX2 cells. • Knockdown of LOXL1 suppressed TGF-β1-induced fibrogenic response. • Knockdown of LOXL1 repressed TGF-β1-induced Smad2/3 phosphorylation. Abstract Liver fibrosis is pathological condition that seriously threatens human health. The lysyl oxidase (LOX) family has been reported to promote liver fibrosis. However, the effect of LOX-like 1 (LOXL1), a member of LOX family, on fibrogenesis of hepatic stellate cells (HSCs) remains unknown. The current study aimed to investigate the role of LOXL1 in liver fibrosis and the potential mechanism. We found that the mRNA and protein levels of LOXL1 were increased in transforming growth factor-beta 1 (TGF-β1)-stimulated human hepatic stellate cell line LX-2. Knockdown of LOXL1 inhibited the proliferation of TGF-β1-stimulated LX-2 cells. Knockdown of LOXL1 suppressed TGF-β1-induced expression of metalloproteinase type 1 (TIMP1), α-smooth muscle actin (α-SMA), and collagen type I (Col-I), as well as phosphorylation of Smad2 and Smad3 in LX-2 cells. In addition, the cell proliferation and fibrogenesis mediated by TGF-β1 stimulation and LOXL1 overexpression were abolished by knockdown of Smad2 and Smad3. Collectively, knockdown of LOXL1 suppressed cell proliferation and fibrogenesis in TGF-β1-stimulated HSCs via regulating the phosphorylation of Smad2/3. [ABSTRACT FROM AUTHOR]

Objectives To investigate the prevalence and associated factors of sarcopenia defined by different criteria in nursing home residents. Design A cross-sectional study. Setting Four nursing homes in Chengdu, China. Participants Elderly adults aged 65 years or older. Measurements We applied 4 diagnostic criteria [European Working Group on Sarcopenia in Older People (EWGSOP), Asia Working Group for Sarcopenia (AWGS), International Working Group on Sarcopenia (IWGS), and Foundation for the National Institutes of Health (FNIH)] to define sarcopenia. Muscle mass, strength, and function were measured based on bioimpedance analysis, handgrip strength, and walking speed, respectively. Nutrition status, activities of daily living, calf circumference (CC), and other covariates were evaluated. Results We included 277 participants. The prevalence of sarcopenia was 32.5%, 34.3%, 38.3%, and 31.4% according to the EWGSOP, AWGS, IWGS, and FNIH criteria, respectively. Fifty-eight participants (20.9%) were sarcopenic by all the 4 criteria. Regardless of the diagnostic criteria of sarcopenia, malnutrition was independently associated with sarcopenia [EWGSOP: odds ratio (OR) 4.02, 95% confidence interval (CI) 1.05-15.39; IWGS: OR 2.46, 95% CI 1.23-4.90; AWGS: OR 3.29, 95% CI 1.49-7.28; FNIH: OR 4.52, 95% CI 1.28-16.00], whereas CC was negatively associated with sarcopenia [EWGSOP: OR per standard deviation (SD) 0.32, 95% CI 0.20-0.52; IWGS: OR per SD 0.26, 95% CI 0.15-0.43; AWGS: OR per SD 0.32, 95% CI 0.19-0.52; FNIH: OR per SD 0.39, 95% CI 0.25-0.60]. Furthermore, falls ≥1 time in the past year were associated with AWGS-defined sarcopenia (OR 2.92, 95% CI 1.04-8.22). Conclusion/Implications Sarcopenia is highly prevalent in elderly Chinese nursing home residents regardless of the diagnostic criteria. Malnutrition and CC are associated with sarcopenia defined by different criteria. Therefore, it is important to assess sarcopenia and malnutrition in the management of nursing home residents. Prospective studies addressing the outcomes of sarcopenia in nursing home residents are warranted. [ABSTRACT FROM AUTHOR]

• Cu-carbene and Mn-carbonyl are good synergistic catalysts for C-C coupling. • The reaction catalyzed by [Mn(CO) 5 ]− belongs the S N 2 mechanism. • Metal carboxyl anions with low nucleophilicity are suitable catalysts. Carbonylative Suzuki-Miyura coupling reaction is one of the most efficient methods to synthetize ketones. In this work, the reaction mechanism of arylboronic esters with alkyl halides catalyzed by Cu/Mn synergistic catalysts has been studied by DFT calculation. The calculated results show that the whole reaction contains two cycles, one is the Cu-catalyzed transformation of Ar-Bneop to RO-Bneop, and the other is Mn-catalyzed Heck–Breslow cycle for alkyl halide carbonylation. At the last step, the final product aryl ketone is produced through the C-C cross-coupling between the two intermediates, which form from the above separate two cycles. For the title reaction, the [Mn(CO) 5 ]− catalyzed the Heck–Breslow cycle belongs to SN 2 mechanism, and Mn 2 (CO) 10 catalyzed cycle is SET mechanism. In addition to [Mn(CO) 5 ]−, the metal carbonyl anions with moderate even low nucleophilicity are suitable to co-catalyze the carbonylative Suzuki-Miyaura coupling with the Cu-carbene catalyst. Our calculation results are consistent with and provide explanations the experimental observations, as well as shed lights on further advancement of new bimetallic catalysts. Reaction mechanism of arylboronic esters with alkyl halides catalyzed by Cu/Mn synergistic catalysts are investigated and metal carbony anions matched Cu-carbene catalyst for C-C coupling are screened. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The structures and properties of hydrogen storage alloy Mg2Ni, of aluminum and silver substituted alloys Mg2−x M x Ni (M = Al and Ag, x = 0.16667), and of their hydrides Mg2NiH4, Mg2−x M x NiH4 (M = Al and Ag, x = 0.125) have been calculated from first-principles. Results show that the primitive cell sizes of the intermetallic alloys and hydrides were reduced by substitution of Mg with Al or Ag. Also, the interaction of Ni–Ni was weakened by the substitution. A strong covalent interaction between H and Ni atoms forms tetrahedral NiH4 units in Mg2NiH4. The NiH4 unit near the Al/Ag atom became tripod-like NiH3 in Mg2−x M x NiH4 (M = Al, Ag), indicating that the hydrogen storage capacity was decreased by the substitution. The calculated enthalpies of hydrogenation for Mg2Ni, Mg2−x Al x Ni and Mg2−x Ag x Ni are −65.14, −51.56 and −53.63 kJ/mol H2, respectively, implying that the substitution destabilizes the hydrides. Therefore, the substitution is an effective technique for improving the thermodynamic behavior of hydrogenation/dehydrogenation in magnesium-based hydrogen storage materials. [ABSTRACT FROM AUTHOR]

Abstract: Ab initio and “Atoms in Molecules” studies have been carried on the intermolecular interactions between oxygen-containing σ-electron donors B (B=H2O, H2CO, (CH2)2O) and hydrogen halide HY and dihalogen molecules XY (X, Y=F, Cl, Br). The geometries, energies and topological characteristics of hydrogen-bonded systems have been compared with those of halogen-bonded systems. In general, many properties of the halogen bond are analogous to those of the hydrogen bond. For the same electron acceptor H or X atom, the properties such as bond distance, binding energy, electron density and charge transfer decrease in the sequence of B···HF>B···HCl>B···HBr, B···ClF>B···Cl2, B···BrF>B···BrCl>B···Br2. The bond distance, frequency shift and electron density may be applied as the measure of strength of hydrogen and halogen bond. The decrease in the atomic dipolar polarization and the atomic volume are dependent of the strength of halogen-bonded interaction, while they are independent of the strength of hydrogen-bonded interaction. [Copyright &y& Elsevier]

Abstract: The reactions of dimethyl sulfoxide (DMSO) with XO (X=NO2, Cl, Br, I) have been studied at CCSD/6-311G(d,p)//B3LYP/6-311G(d,p) level. Two reaction channels have been considered: (1) the oxygen-atom transfer (OAT) from XO (X=NO2, Cl, Br, I) to DMSO and (2) the hydrogen-abstraction by XO (X=NO2, Cl, Br, I). The reaction mechanisms of DMSO with NO3, ClO and BrO are similar: the OAT channel is the dominant channel and DMSO2 is the primary product; the hydrogen-abstraction channel is not likely to be competitive with the OAT channel. The DMSO+IO reaction, because two reaction channels have the overall negative reaction activation energies and Gibbs free energies, the reaction could occur on both reaction channels. Furthermore, the formation of the stable complex may vary the yield rate of DMSO2. [Copyright &y& Elsevier]

Abstract: The reactions of SSHX to HSSX (X=F, Cl, Br and I) have been studied at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(2df,pd) level. The Sh name="sbnd" />H and Sh name="sbnd" />X ring structure transition region (STR) and respective structure transition state (STS) have been studied in the framework of the “Atoms in Molecules” theory. The following conclusions are drawn: (a) For the Sh name="sbnd" />H and Sh name="sbnd" />X ring structures, according to the sequence of X=F, Cl, Br and I, the STR becomes broader and the STS appears later. (b) For the H atom transfer pathway and X atom transfer pathway, the lower the energy barrier is, the broader the ring STR (Sh name="sbnd" />H ring STR or Sh name="sbnd" />X ring STR) is and the later the STS appears. [Copyright &y& Elsevier]

The reactions of BrNCO to BrOCN, BrNCS to BrSCN and BrNCSe to BrSeCN have been studied at MP2/6-311++G(2df)//B3LYP/6-311++G(2df) level. Geometries of the reactants, transition states and products have been optimized and geometries of the transition states are found for the first time. The reasons of why BrNCO, BrSCN and BrSeCN are easily detected instead of BrOCN, BrNCS and BrNCSe have been explained successfully. The breakage and formation of the chemical bonds in the reactions have been discussed by the topological analysis method of electronic density. The calculated results show that there are two kinds of structure transition states in topic reactions. [Copyright &y& Elsevier]

Mechanisms of RN3 (R=CH3, CH3CH2, (CH3)2CH, (CH3)3C) dissociations are proposed based on CAS, MP2 and B3LYP methods. The energy gaps between the ground-state reactants RN3 and the intersystem crossing (ISC) points are only a little lower than respective potential energy barriers of the spin-allowed reactions, 1RN3 → 1RN + 1N2. The ISC point, therefore, is considered as a transition state of the spin-forbidden reactions, 1RN3 → 3RN + 1N2. The methods of IRC and topological analysis of electron density are used to explain and predict the thermal dissociation pathways of the reactions studied. [Copyright &y& Elsevier]

Mechanisms of XN3 (X: F, Cl, Br, I) dissociations are proposed based on B3LYP calculated potential energy surfaces. The energy gaps between the ground-state reactants XN3(x˜ 1A′) and the intersystem crossing (ISC) points are only a little lower than respective potential energy barriers of the spin-allowed reactions, XN3(x˜ 1A′)→XN(a 1Δ)+N2(x˜ 1Σg+). The ISC point, therefore, is considered as a ‘transition state’ of the spin-forbidden reactions, XN3(x˜ 1A′)→XN(x˜ 3Σ−)+N2(x˜ 1Σg+). The methods of IRC and topological analysis of electron density are used to predict the thermal dissociation pathway of the reactions studied. [Copyright &y& Elsevier]

Background: Nurses in the intensive care unit have a high incidence of occupational burnout, which has a serious adverse impact on their physical and mental health. It is imperative, therefore, to explore interventions, especially those that may enhance individual coping resources. Mindfulness has been proven to be one such effective resource. The purpose of this study was to explore the effect of an eight-week mindfulness intervention on occupational burnout in ICU nurses.Methods: One hundred six nurses in two ICUs who met the inclusion criteria were recruited to the program, which consisted of an educational intervention related to burnout (EB, n = 53) or a mindfulness-based intervention (MBIB, n = 53), and the results compared. The Maslach Burnout Inventory (MBI), the Mindfulness Attention Awareness Scale (MAAS), and the Acceptance and Action Questionnaire II (AAQ-II) were administered at T0 (before the intervention), T1 (one week after the intervention), T2 (one month after the intervention), and T3 (three months after the intervention). A total of 91 nurses completed the study. Data were analysed by intention-to-treat analysis and repeated-measures ANOVA to observe the effects of the mindfulness-based intervention on occupational burnout.Results: Nurses' mindfulness, experiential avoidance, emotional exhaustion, depersonalization, and personal accomplishment were all affected by the intervention. The effect could be maintained to the third month post intervention.Conclusion: Mindfulness-based intervention can effectively improve the level of mindfulness and decrease the level of experiential avoidance among ICU nurses, alleviating occupational burnout. [ABSTRACT FROM AUTHOR]

The reaction of Cl atoms with two C 5 aldehydes (3-methyl-2-butenal and 3-methylbutanal) were investigated by proton-transfer-reaction mass spectrum (PTR-MS) using smog chamber at 298 ± 1 K and 760 Torr. A relative rate method was used to determine the rate constants of the title reactions with m -xylene and trans -2-butene as reference compounds: (3.04 ± 0.18) × 10−10 and (2.07 ± 0.14) × 10−10 cm3/(molecule⋅sec) for 3-methyl-2-butenal and 3-methylbutanal, respectively. Additionally, the gas-phase products were also identified by PTR-MS, and the possible reaction mechanisms were proposed basing on the identified products. The detected gas-phase products are similar for two C 5 aldehydes reactions, mainly including small molecules of aldehydes, ketones and chlorinated aldehyde compounds. The atmospheric lifetimes (τ) calculated for 3-methyl-2-butenal (τ = 7.0 hr, marine boundary layer (MBL)) and 3-methylbutanal (τ = 10.3 hr, MBL) according to the obtained rate constants. The results indicate that Cl atoms at MBL are competitive with OH radicals for the degradation contribution of C 5 aldehyde compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

• Cp 2 Nb(CO)H can react with ADCA easily even at low temperature. • k 1-pro is the most stable product thermodynamically. • The yield rate of (E)-pro is larger than that of (Z)-pro in this reaction. • A η 2-(C1, C2)-Nb agostic bonding exists in the reaction pathway. The insertions of unsaturated molecules into metal-hydride bonds are very common steps in industrial catalytic reactions such as olefinic isomerization, hydrogenation and hydroformylation. In this paper, the reaction mechanism of Cp 2 Nb(CO)H (Cp = η 5-C 5 H 5) with acetylenedicarboxylic (ADCA) has been investigated based on density functional theory calculations. Kinetic calculation and topological analyses of electron density have been conducted. The calculated results show that the reaction can proceed easily even at very low temperature. (Z)-pro Cp 2 Nb(CO)(η 1-(Z)–HOOCC = CHCOOH) and the isomer (E)-pro can be got via two parallel steps. The yield rate of (E)-pro is larger than that of (Z)-pro because of its lower energy barrier. In addition, the carboxylato-containing niobocene compound Cp 2 Nb(CO)(k 1-OOCC(H)= CHCOOH) can also be got as the most stable product through a proton transfer process. Along the reaction pathway, there is a η 2-(C, C)-Nb agostic structure. The results provide useful informations and theoretical predictions on much more insertion reactions. [ABSTRACT FROM AUTHOR]

The binding mechanism and binding forces of API-CCF cocrystal with BSA and cell inhibitory rates vary with the kinds of weak forces between API and CCF. • Novel curcumine(CUR)-isonicotinamide (1) and CUR-gallic acid (2) cocrystals were prepared. • C O and O H groups in CUR involved in the hydrogen bonds in cocrystal 1 and 2, respectively. • Hydrogen bonds and/or van der Waals forces occurred between cocrystal 1 and BSA binding reaction. • Hydrophobic forces occurred in the binding reaction with BSA for cocrystal 2. • Cell inhibitory rates of cocrystal 1 differed from that of cocrystal 2. Screening of cocrystal has been proved to be a powerful approach to improve the solubility, dissolution rate and even the bioavailability of poorly water-soluble active pharmaceutical ingredient (API). Typically, the formation of cocrystal induces no change on the pharmacological profile of the APIs. However, so far, it is not clear whether a cocrystal would induce changes in biological profiles of API and, if so, which factors induce those changes. To clarify these aspects, two CUR-isonicotinamide (cocrystal 1) and CUR-gallic acid (cocrystal 2) cocrystals with enhanced physical properties and pharmacokinetic profile for potential pharmaceutical application were screened. We focused on the effects of the type of hydrogen bonds occurred in cocrystal on the binding between cocrystal and BSA as well as cell inhibiting activity. The appearance of new peaks in the X-ray powder diffraction (PXRD) and a single different melting point in the differential scanning calorimetry (DSC) measurements revealed that homogeneous, single phase formulations were obtained by forming cocrystals between CUR and coformers in a 1:2 M ratio. The results of Fourier-transform infrared and solid-state 13C nuclear magnetic resonance spectra as well as density function theory simulation indicated that different hydrogen bonds were formed in two cocrystal, which were the C O⋯H N hydrogen bond between the C O group in CUR and the N H groups in isonicotinamide in cocrystal 1, and C O⋯H O hydrogen bond between phenol O H group in CUR and the C O group in gallic acid in cocrystal 2, respectively. Interestingly, the different type of weak interactions in cocrystal induced various binding pattern between cocrystal and BSA and cancer cell cytotoxicity supported by fluorescence spectroscopy and MTT assay in vitro. It was reasonable that the affinity of cocrystal for proteins varied with specific and concerted weak interactions in cocrystal, which would induce changes in the biological profiles of the parent drug. Furthermore, in vivo pharmacokinetics of CUR and CUR-based cocrystals in SD rats were evaluated through UPLC-MS/MS method. Compared with intact CUR, the pharmacokinetics parameters C max , T max , AUC 0-t and AUC 0-∞ of CUR-based cocrystals were improved (P < 0.05); C max increased 30-fold, T max shortened 6-fold, and AUC 0-t increased 6-fold. Overall, the present results inferred different effects induced by cocrystals on a biologic system, not only bioavailability but biological profiles. [ABSTRACT FROM AUTHOR]

Background GHET1 is one of tumor-related lncRNAs. We aimed to explore the functional involvement of GHET1 in hepatocellular carcinoma (HCC). Methods In this study, HCC tissues and the paired normal tissues were collected for the detection of target molecules. The expression level of target molecules in HCC tissues or cell lines was determined by qRT-PCR and western blot, respectively. The expression of endogenous GHET1 and ATF1 was modulated by using cell transfection. RNA pull down assay was performed to examine the interaction between GHET1 and ATF1. ChIP assay was conducted to determine the H3K27Ac acetylation of GHET1 promoter. Results H3K27 acetylation activated-GHET1 was upregulated in HCC tissues and cell lines. Moreover, GHET1 silencing could inhibit the proliferation, migration, invasion and EMT of HCC cells in vitro . GHET1 could regulate the expression of ATF1 mRNA and protein; RNA pull-down assays supported that GHET1 could bind to ATF1 protein. Furthermore, overexpression of ATF1 almost completely reversed the GHET1 knockdown mediated inhibition on the proliferation, migration, invasion and EMT of HCC cells. Conclusion LncRNA GHET1 was intimately involved in the occurrence and development of HCC through regulating ATF1. [ABSTRACT FROM AUTHOR]

The electronic structures, dehydrogenation properties and diffusion path of an H atom in pure and transition metal substituted Mg(BH 4 ) 2 ·2NH 3 were investigated using the first-principles calculations. The occupation energies of dopants indicate that substituting Ti for an Mg1 atom is the easiest, while Ni and Nb substitutions are somewhat difficult. The electronic density of states and the topological analysis of electron density reveal the covalent characteristics of the N–H and B–H bonds and the weak ionic interaction between M (the metal atoms) and the NH 3 and BH 4 groups. The substitutions of Ti, Ni and Nb increase the interaction between metal and N atoms, which stabilize the NH 3 groups and inhibit the release of ammonia during dehydrogenation. The hydrogen removal energies indicate that Ti, Ni or Nb doping weakens the interactions between B and H atoms, thereby facilitating the dissociation of B–H bonds in Mg(BH 4 ) 2 ·2NH 3 . The minimum energy paths of H diffusion demonstrate that the substitutions can reduce the energy barrier and thus favor H diffusion in the bulk phase. Thus, substitution is an effective technique for improving the hydrogenation/dehydrogenation performance of Mg(BH 4 ) 2 ·2NH 3 hydrogen storage material. [ABSTRACT FROM AUTHOR]

The electronic structures and bonding characters, the occupation energies of dopants, as well as the formation energies of Frenkel defects in pure LiBH 4 ·NH 3 and in Mg- and Al-substituted LiBH 4 ·NH 3 were investigated by using first-principles calculations. The occupation energies show that the substitutions with Mg and Al destabilize LiBH 4 ·NH 3 and that Mg substitution is easier than Al substitution. Substitution with Mg or Al partly reduced interactions between B–H and N–H atoms, thus improving the dehydrogenation property of LiBH 4 ·NH 3 . At the same time, substitution with Mg or Al increases the interactions between metal and N atoms, which stabilize the NH 3 group and inhibit the release of NH 3 during dehydrogenation. The formation energy of Frenkel defects indicates that Mg or Al doping facilitates the formation of Frenkel defects. Our theoretical studies show that Mg and Al are good candidates but Al is better than Mg for improving the dehydrogenation property of LiBH 4 ·NH 3 . [ABSTRACT FROM AUTHOR]

Abstract: The structures and dehydrogenation properties of pure and Ti/Ni-doped Mg(AlH4)2 were investigated using the first-principles calculations. The dopants mainly affect the geometric and electronic structures of their vicinal AlH4 units. Ti and Ni dopants improve the dehydrogenation of Mg(AlH4)2 in different mechanisms. In the Ti-doped case, Ti prefers to occupy the 13-hedral interstice (TiiA) and substitute for the Al atom (TiAl), to form a high-coordination structure TiH n (n = 6, 7). The Ti 3d electrons hybridize markedly with the H 1s electrons in TiAl and with the Al 3p electrons in TiiA, which weakens the Al–H bond of adjacent AlH4 units and facilitates the hydrogen dissociation. A TiAl3H13 intermediate in TiiA is inferred as the precursor of Mg(AlH4)2 dehydrogenation. In contrast, Ni tends to occupy the octahedral interstice to form the NiH4 tetrahedron. The tight bind of the Ni with its surrounding H atoms inhibits their dissociation though the nearby Al–H bond also becomes weak. Therefore, Ti is the better dopant candidate than Ni for improving the dehydrogenation properties of Mg(AlH4)2 because of its abundant activated hydrogen atoms and low hydrogen removal energy. [Copyright &y& Elsevier]

Abstract: The crystal and electronic structures, the formation energy of H vacancies, and the diffusion path of the H atom (i.e., diffusion path of H vacancy) in unsubstituted and substituted LiNH2 crystal were investigated by periodic first-principles calculations. The bonding characters between atoms were studied by topological analysis of electron density. Our calculations reveal that substitution of the Li atom with Ti or Nb favors the formation of hydrogen vacancies adjacent to substitution, and the existence of an H vacancy and Ti or Nb substitution can cause weakening of nearby N–H bonds, which facilitates N–H bond dissociation. The minimum energy paths of H diffusion show that the substitution can reduce the energy barrier and thus favor H diffusion in the bulk phase of LiNH2. [Copyright &y& Elsevier]