The Structures and Stability of HNOS Isomers

Potential energy surface of HNOS system is investigated by means of MP2 method with 6-311 G(d,p) basis set.The energy for each minimum and saddle point on the potential energy surface is corrected at the QCISD(T)/6-311 G(3df,2p) level of theory with zero-point vibrational energy included.As a result ,eighteen isomers are theoretically predicted and cis-HNSO is found to be global minimum on the potential energy surface,Wherein,fourteen isomers are considered as kinetically stable species,and should be experimentally observed.Comparisons are made for HNOS system with its analogues,HNO2 and NHS2.The nature of bonding and isomers‘ stability of HNOS system are similar to HNS2.The obvious similarities and discrepancies among HNOS,HNO2 and HNS2 are attributed to the hypervalent capacity of sulfur,oxygen and nitrogen atoms.     

Structures and Stability of NHS2 Isomers

Potential energy surface of HNS2 is investigated by means of second-order Moller-Plesset Perturbation theory(MP2) and QCISD(T) (single-point)methods,At final QCISD (T)/6-311 G(3df,2p)//MP2/6-311 G(d,p),level with zero-point vibrational energies included,cis-NHSS is found to be global minimum on the potential energy sufrace,followed by low-lying trans-HNSS ,HN(S)S(C2v).cis-HSNS,cis-NSSN,trans-HSNS,trans-NSSN,and HN(S)S(Cs) by 13.46,66.92,78.25,80.38,81.22,81.38 and 86.40 kJ/mol,respectively.A new high-lying HS(N)S isomer with Cs symmetry is located on the potential energy surface ,The kinetic stabilities of all isomers are predicted.Comprisons are made for HNS2 with its analogues,NHO2,HPS2 and HPO2,The causes that lead to the differences between HNS2 and its analogues are hypervalent capacity of phosphorus and distinct electronegativities of hydrogen,nitrogen and phosphorus.     

Structures and Stability of HNS_2 Isomers

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Structure and Stability of Isomers of the Promising Interstellar Molecule PC3O

DFT/B3LYP/6-311G(d) and CCSD(T)/6-311G(2d) single-point calculations are carried out for exploring the doublet potential energy surface (PES) of PC₃O, a molecule of potential interest in interstellar chemistry. A total of 29 minima connected by 65 interconversion transition states are located. The structures of the most relevant isomers and transition states are further optimized at the QCISD level followed by CCSD(T) single-point energy calculations. At the CCSD(T)/6-311G(2df)//QCISD/6-311G(d)+ZPVE level, the global minimum is the quasi-linear structure PCCCO 1 (0.0 kcal/mol) with a great kinetic stability of 47.9 kcal/mol, and the cumulenic form features largely in its resonance structures. Moreover, the chainlike isomer OPCCC 3 (64.5) and five-membered-ring species cPCCCO 19 (77.8) possess considerable kinetic stability of about 18.0 kcal/mol. All these three isomers are very promising candidates for future experimental and astrophysical detection. Additionally, a three-membered-ring isomer CC-cCOP 10 (69.6) has slightly lower kinetic stability of around 15 kcal/mol and may also be experimentally observable. Possible formation mechanisms of the four stable isomers in interstellar space are discussed. The present research is the first attempt to study the isomerization and dissociation mechanisms of PC _n O series. The predicted spectroscopic properties, including harmonic vibrational frequencies, dipole moments and rotational constants for the relevant isomers, are expected to be informative for the identification of PC₃O in laboratory and interstellar medium.     

Singlet H-cCNC-C：A Potential Interstellar Molecule

A new planar isomer of HNC3 system,H-cCNC-C,is theoretically predicted by means of B3LYP and CCSD(T) methods.The suggested species can isomerize into other five kinetically more stable isomers,which have been experimentally identified,with relatively higher reaction barriers.In view of its higher kinetic stability,we can reasonably believe that the obtained species H-cCNC-C can be experimentally observed in future studies.     

Structures and stabilities of HPO_2 isomers

The potential energy surface of HPO2 system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energy surface, cis-HOPO(E1) is found to be thermodynamically and kinetically most stable isomer followed by trans-HOPO(E2) and HPO(O)(C2v, E3) at 10.99 and 48.36 kJ/mol higher, respectively. Based on the potential energy surface, only E1 and E3 are thermodynamically stable isomers, and should be experimentally observable. The products cis-HPOO(E5) and frans-HPOO(E6) in the first-step reaction of HP with O2 can isomerize into isomer E1 that has higher stability. The reaction of OH with PO will directly lead to the formation of isomer E1. The computed results are well consistent with the previous experimental studies.     

Structures and stabilities of HPS_2 isomers

The potential energy surface of HPS2 system containing nine isomers and fifteen transition states is obtained at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df, 2p)(single-point) levels. On the potential energy surface, the lowest-lying frans-HSPS(EI) is found to be thermodynami-cally the most stable isomer followed by cis-HSPS(E2) and HP(S)S(C2v, E3) at 3.43 and 14.17 kJ/mol higher, respectively. The computed results show that species E1, E2, E3, stereo HP(S)S(Cs, E4) with PSS three-membered ring, isomers trans-HPSS(E5) and cis-HPSS(E6) which coexist with E4 are kinetically stable isomers. The products E6 and E5 in the reaction of HP with S2 can be isomerized into higher kinetic stable isomer E4 with 65.75 and 71.73 kJ/mol reaction barrier height, respectively. The predicated results may correct the possible inaccurate conclusion in that the product was experimentally assigned as isomer cis-HPSS(E6).     

HPOS体系异构体结构与稳定性

在MP2／6－311＋＋G(d,p)和QCISD（T）／6－311＋＋G（3df,2p)（单点）水 平下计算得到了HPOS体系势能面上18个异构体和25个过渡态及解离碎片等驻点，并 分析了这些异构体的结构及异构化过程，讨论了可能的解离方式。在得到的异构体 中，有8个异构体是动力学较稳定的，它们是dis-HOPS,trans-HOPS,trans-HSPO, cis-HSPO,HP(O)S(Cs),trans-HPSO,cis-HPSO和HP（O）S（C1）。这些异构体在实 验中应该可以观测到。理论研究表明，P与S原子较强的超价能力在降低异构体能量 ，提高异构体动力学稳定性方面起到了关键的作用。得到的计算结果与HPO2， HPS2，HNOS等价电子相同的体系进行了比较。     

HAsO~2异构体结构、相对稳定性与体系势能面

在MP2/6-311++G(d,p)和QCISD(T)/6-311++G(3df,2p)(单点)水平下计算得到了包括9个异构体和10个过滤态的HAsO~2体系势能面。在势能面上，异构体cis-HOAsO(E1)的能量是最低的，其次是trans-HOAsO(E2)和HAsO(O)(C~2~V,E3)，能量分别比cis-HOAsO高13.15和192.74kJ/mol。根据体系的势能面，异构体E1，E3及cis-HOOAs(E6),trans-HOOAs(E5)具有一定的动力学稳定性，在实验中应该可以观测到。AsH和O~2反应的第一步产物将会异构化为具有较高动力学稳定性的异构体E3；而OH和AsO反应可直接生成E1。计算结果与HPO~2,HPS~2,HNO~2,HNS~2等价电子相同的分子的势能面进行了比较。     

Theoretical Study on the Structures and Stability of Isomers and Complex of[Si,C,O,O] Sytem

A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies.     

Theoretical Study on the Structures and Stability of Isomers and Complex of [Si, C, O, O] System

Introduction[Si,C ,O ,O]systemhasattractedmuchattentioninthefieldsofchemistryandmaterials1 3becauseofthefollow ingseveralcauses .First,theinterestisthepotentialimpor tanceininterstellarspace .Heretofore ,SiC ,SiOandCOhavebeendetectedwithintheinterstellarmediumformanyyears,butno [Si,C ,O ,O]isomerswereobservedinthenebulae .FormanySi containingsystemshavebeenstudiedexperimentallyandtheoretically ,4 8andinviewofthepossibleexistenceofthe [Si,C ,O ,O]radicalininterstellarspace ,weselectthe…     

Synthesis of Highly Charged C3-Symmetrical Organic Molecule with a Fused Planar Core Structure

A new C3-symmetric molecule integrated with a number of interesting features, including three highly charged and flexible pyrrolidinium arms extending from a fused planar core structure, is synthesized.     

S3分子的结构与最可几解离过程理论研究

用量子化学从头算方法,计算得到了S3分子优化的几何结构(基态和几个低激发态);研究了其在C2v与Cs群对称性下的解离过程,给出两种群对称性下基态和激发态的势能曲面及等高投影图;在两种群对称性下均得到在相应势能曲面上的优化的解离路径.     

Theoretical Studies on Structure,Isomerization, and Stability of [Si,O, S]

The structures, energetics, and isomerization of a possible interstellar [Si, O, S] system were explored at the CCSD(T)/aug-cc-pVQZ//CCSD(T)/aug-cc-pVTZ level. On the schemaitc potential energy surface(PES), we found that silicon oxysulfide(OSiS) produced in laboratory is the global minimum. An analysis of the Wiberg bond index(WBI), bond order and the bond length, shows that silicon oxysulfide contains SiO and SiS double bonds in accordance with the results of Schn?ckel. Besides silicon oxysulfide, another interesting cyclic minimum(c-SiOS) was found to have a very high kinetic stability stabilized by the least barrier of 120.9 kJ/mol. In light of the fact that no cyclic sulfide-containing species has been detected in space, c-SiOS could be a very promising candidate. The presented results might provide useful information on detected interstellar molecules O=Si=S and c-SiOS.     

HPO3异构体结构与稳定性

使用密度泛函方法(B3LYP)和6-311 G(3df,3pd)基组计算得到了HPO3体系的9个异构体与11个过渡态,并用内禀反应坐标理论验证了异构体的异构化过程．结果表明,在HPO3体系中,只有热力学最稳定的平面型异构体HOFO2(E1),(cis,cis)构象的HOOPO(E3)和立体的具有Cs对称性的异构体HP(O)O2(E7)具有较高的动力学稳定性,理论预测结果与实验一致．另外2个立体的HOFO2连接方式的异构体(E2和E4)由于解离为HO(Ⅱ) OPO(^2A1)的解离能较低,因此不能稳定存在。     

Structures and stabilities of HPS2 isomers

The potential energy surface of HPS² system containing nine isomers and fifteen transition states is obtained at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df, 2p)(single-point) levels. On the potential energy surface, the lowest-lying trans-HSPS(E1) is found to be thermodynamically the most stable isomer followed by cis-HSPS(E2) and HP(S)S(C_2v, E3) at 3.43 and 14.17 kJ/mol higher, respectively. The computed results show that species E1, E2, E3, stereo HP(S)S(C_s, E4) with PSS three-membered ring, isomers trans-HPSS(E5) and cis-HPSS(E6) which coexist with E4 are kinetically stable isomers. The products E6 and E5 in the reaction of HP with S² can be isomerized into higher kinetic stable isomer E4 with 65.75 and 71.73 kJ/mol reaction barrier height, respectively. The predicated results may correct the possible inaccurate conclusion in that the product was experimentally assigned as isomer cis-HPSS(E6).     

Structures and stabilities of HPO<Subscript>2</Subscript> isomers

The potential energy surface of HPO₂ system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energy surface, cis-HOPO(E1) is found to be thermodynamically and kinetically most stable isomer followed by trans-HOPO(E2) and HPO(O)(C_2v, E3) at 10.99 and 48.36 kJ/mol higher, respectively. Based on the potential energy surface, only E1 and E3 are thermodynamically stable isomers, and should be experimentally observable. The products cis-HPOO(E5) and trans-HPOO(E6) in the first-step reaction of HP with O₂ can isomerize into isomer E1 that has higher stability. The reaction of OH with PO will directly lead to the formation of isomer E1. The computed results are well consistent with the previous experimental studies.     

HNO2异构体及其相互转化反应机理的量子化学研究

NO在对流层和平流层的光化学过程起重要作用。HO自由基在清除大气污染物和生成臭氧过程中起着关键作用。HO自由基与NO反应生成非常活泼的自由基HONO,这在气相化学中具有重要地位。Cleaner等发现HNO2存在多种异构体,这些异构体间怎样转化以及其能否稳定存在的问题非常重要。     

Structure and Stability of C20H3 Radical

Density functional theory B3LYP with 6-31G* basis set has been used to investigate the geometries, rotational constants, dipole moments, energy gaps and vibrational frequencies of nine series of isomers of C20H3 radical. The result shows that the bowl-like structure with C1 symmetry is the most stable structure, in which the three hydrogen atoms locate on the edge carbon atoms, and the two hydrogen atoms are neighbouring and the other one has a two- carbon atom interval to the neighbouring hydrogen. In addition, the relationship between the energy and the position of one hydrogen atom from end to middle on the linear structures of C20H3 radical with two hydrogens atoms located on two ends was obtained, which shows the energy increase monotonously. Furthermore, hydrogenation can relax the strain and make the isomer of C20 more stable.     

[GeCN2]分子异构化势能面的理论研究

在CCSD(T)/6-311＋G(2df)//B3LYP/6-311＋G(d)水平下, 研究了四原子分子 [GeCN2]的各个异构体的几何结构、红外振动光谱、相对能量及异构化和解离稳定性, 构建了[GeCN2]势能面. 我们得到了7个[GeCN2]异构体, 包括5个直线型结构GeNCN (1), GeNNC (2), NGeCN (3), NGeNC (4), GeCNN (5)和2个环形结构Ge-cCNN (6)和Ge-cNCN (7). 其中异构体5, 6, 7是我们新找到的构型, 而且GeCNN (5)是整个势能面上稳定性仅次于GeNCN (1)的异构体. 几何和电子结构分析表明, GeCNN (5)具有共轭三键结构: Ge≡C—N≡N:. 由于具有良好的热力学和动力学稳定性, 异构体GeCNN (5)有望在实验中观测到. 我们建议利用过渡金属羰基化合物的络合作用可以进一步稳定GeCNN (5). 本研究为寻找新型含高周期元素的多重键化合物提供了理论线索.