化学学报
化學學報
화학학보
ACTA CHIMICA SINICA
2001年
2期
179-184
,共6页
虞忠衡%彭晓琦%郭彦伸%宣正乾
虞忠衡%彭曉琦%郭彥伸%宣正乾
우충형%팽효기%곽언신%선정건
定域轨道基组%片断轨道%微扰分子轨道理论%轨道定域化
定域軌道基組%片斷軌道%微擾分子軌道理論%軌道定域化
정역궤도기조%편단궤도%미우분자궤도이론%궤도정역화
高度定域的、对称的、键轨道基组的建立是一个多步的计算程序:(1)以定域片断轨道[Фk,Фi,φj]为基,对分子作有条件的RHF运算,算得FUL和DSI°态的片断分子轨道[Ф0l,Ф0n,Ф0m]和[Фl,Фn,Фm].在基组[Фk,Фi,φj]中,Фi∈双占据和空σ片断分子轨道(FMOs)组,φi∈πFMO组,Фk∈单占据σFMO组,它们都精确地定域在各自的片断内;(2)利用Ф0l与Фl间的重叠积分值(Sll>O.5),可以从DSI°态中,自动地选出Ns个对称的、由单占据轨道线性组合而成的分子轨道Ф0l=∑akФk(k=1,2,…,Ns).接着,用Ф0l取代FUL态中同类的、非对称轨道组Фl=∑aldФk(k=1,2,…,Ns);(3)以上述新的轨道组[Ф0l,Фn,Фm]为基(其中,Ф0l∈DSI0态,它们离域于整个分子;双占据及空σFMO组Фn和πFMO组Фm属于FUL态),按FUL态的条件,再次对分子作有条件的RHF运算,从中得到一组对称的、闭壳层正则FMOs,而且每一个FMO均有正确的电子占据数;(4)利用Perkin原理,将第3步所得的正则FMO组定域成一个对称的键轨道基组[Фl′,Фn′Фm′].在这个基组中,π体系Фm′与σ构架Фn′是彻底分离的,而且这两个轨道组始终精确地定域在各自的片断内.
高度定域的、對稱的、鍵軌道基組的建立是一箇多步的計算程序:(1)以定域片斷軌道[Фk,Фi,φj]為基,對分子作有條件的RHF運算,算得FUL和DSI°態的片斷分子軌道[Ф0l,Ф0n,Ф0m]和[Фl,Фn,Фm].在基組[Фk,Фi,φj]中,Фi∈雙佔據和空σ片斷分子軌道(FMOs)組,φi∈πFMO組,Фk∈單佔據σFMO組,它們都精確地定域在各自的片斷內;(2)利用Ф0l與Фl間的重疊積分值(Sll>O.5),可以從DSI°態中,自動地選齣Ns箇對稱的、由單佔據軌道線性組閤而成的分子軌道Ф0l=∑akФk(k=1,2,…,Ns).接著,用Ф0l取代FUL態中同類的、非對稱軌道組Фl=∑aldФk(k=1,2,…,Ns);(3)以上述新的軌道組[Ф0l,Фn,Фm]為基(其中,Ф0l∈DSI0態,它們離域于整箇分子;雙佔據及空σFMO組Фn和πFMO組Фm屬于FUL態),按FUL態的條件,再次對分子作有條件的RHF運算,從中得到一組對稱的、閉殼層正則FMOs,而且每一箇FMO均有正確的電子佔據數;(4)利用Perkin原理,將第3步所得的正則FMO組定域成一箇對稱的鍵軌道基組[Фl′,Фn′Фm′].在這箇基組中,π體繫Фm′與σ構架Фn′是徹底分離的,而且這兩箇軌道組始終精確地定域在各自的片斷內.
고도정역적、대칭적、건궤도기조적건립시일개다보적계산정서:(1)이정역편단궤도[Фk,Фi,φj]위기,대분자작유조건적RHF운산,산득FUL화DSI°태적편단분자궤도[Ф0l,Ф0n,Ф0m]화[Фl,Фn,Фm].재기조[Фk,Фi,φj]중,Фi∈쌍점거화공σ편단분자궤도(FMOs)조,φi∈πFMO조,Фk∈단점거σFMO조,타문도정학지정역재각자적편단내;(2)이용Ф0l여Фl간적중첩적분치(Sll>O.5),가이종DSI°태중,자동지선출Ns개대칭적、유단점거궤도선성조합이성적분자궤도Ф0l=∑akФk(k=1,2,…,Ns).접착,용Ф0l취대FUL태중동류적、비대칭궤도조Фl=∑aldФk(k=1,2,…,Ns);(3)이상술신적궤도조[Ф0l,Фn,Фm]위기(기중,Ф0l∈DSI0태,타문리역우정개분자;쌍점거급공σFMO조Фn화πFMO조Фm속우FUL태),안FUL태적조건,재차대분자작유조건적RHF운산,종중득도일조대칭적、폐각층정칙FMOs,이차매일개FMO균유정학적전자점거수;(4)이용Perkin원리,장제3보소득적정칙FMO조정역성일개대칭적건궤도기조[Фl′,Фn′Фm′].재저개기조중,π체계Фm′여σ구가Фn′시철저분리적,이차저량개궤도조시종정학지정역재각자적편단내.
A procedure for constructing a highly localized and symmetrical bond orbital basis set with the πsystems separated off from the σ frameworks has been developed. It is a four- step procedure: ( 1 )over the opened-shell localized fragment molecular orbital (FMO) basis set [φk, φi, φj] where φi ∈ doubly occ. And vacant σFMOs, φj ∈ πFMOs, and φk ∈ singly occ. FMOs, the conditional RHF computations provide each of the FUL and DSI° electronic states of a molecule, such as norbornadiene with a set of the closed-shell FMOs;(2) the symmetrical MOs, φ0l′= ∑ akl′ φk ( k = 1,2,…, Ns) which have delocalized over the whole molecule, in the DSI° substitutes for the unsymmetrical Фl = ∑aklφk in FUL state, and those together with other two groups of the unsymmetrical FMOs, Фm= ∑ajmφj and Ф′n = ∑ainφi in the FUL state formed a closed-shell FMO basis set [Фn, Фm,Ф0l′ ] in which each of FMOs Фn and Фm is still localized On its corresponding fragment;(3) based on the basis set [ Фn, Фm, Ф0l′ ], the conditional RHF computation for molecule is performed under the following constraint: all Fij =0.0 and Sij =0.0( i ≠ j, i ∈ fragment P, j∈ fragment Q, and P ≠ Q )except for those between Ф0l′. It provides a molecule, such as norbornadiene, with a highly localized and symmetrical FMO basis set [Фb′, Фm′ ,Ф1′ ]; (4)each of the FMOs Фn′, Фm′ and Ф1′ is concentrated on a specific atom or two neighboring atoms using the Perkin procedure at last, and it has correct orbital occupancy.