计算机模拟分子材料

计算机模拟与材料分子设计

ComputerSimulationandMolecularDesign

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

Lecture5

势能面的构筑及其最新动态

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

势能面

到整廊是一种数学函数用来描述分子的能量

与其几何结构之间的关系。

•分子力学是把能量作为伸缩，弯曲，扭转

等的函数。这个近似模型不能描述化学键断

裂等情况，而且需要有合适的参数。

•量子力学给出一个能量函数适用于任何分

子，但是实际上使用的仍是近似的量子力学

模型以降低计算消耗。

；')DalianUniversity

yofTechnologyGraduateCourse,Lecture52010Autumn

最简单的一维势能面

StandardDiatomicBondStretch

B

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

一般势能面的维数

•一般情况下势能面究竟有几维呢？定义一

个厚子的位置，原则上只需在三维空间里

取三个坐标(egx,y,andz)o

•但是，势能面不能取决于原子的绝对位置,

而取决于其相对于周围其他原子的位置

(i.e.Moleculargeometry)

•因此，典型的势能面的维数应该等于分子

的自由度数(3N-6,N为原子数且大于2,分

子为非线性)

；')DalianUniversity

yofTechnologyGraduateCourse,Lecture52010Autumn

Exampleofpotentialenergysurface

globalmaximum

localmaximum

localminimum

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

StationarypointsonPES

>Stationarypointsinclude:

•Localminimum&Globalminimum

(equilibriumstructure,correspondingto

reactant,product,intermediate)

•Saddlepoint

(transitionstate,transitionstructure,

correspondingtotransitionstate)

•Localmaximum&Globalmaximum

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

SlicesofPotentialEnergySurface

由于多维势能面很难图示化，常取势能面的一部分

Here,wetakeatwo-

dimensionalslice(the

mostwecaneasily

graph,sinceenergyisthe

thirdccx>rdinate)ofa

moleculewith3degrees

offreedom;itisthebond

anglethatisbeingheld

fixedthatdefinesthe

slice.

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

进一步理解势能面

・势能面不体现动能

•在T=0K(noKineticEnergy),分子将倾

向于处在最低势能的状态，比如势能面上

的极小值(Minimum)。有效地找到这些极小

值的方法是很有意义的。

•在两个极小值之间(valleybottoms)的最小

能路径将通过一个鞍点(saddlepoint),在

化学上我们称作该点的结构为过渡态结构,

找到过渡态也是很有意义的。

；')DalianUniversity

yofTechnologyGraduateCourse,Lecture52010Autumn

势能面片段

_Rateconstantforaminimum

“passingthroughatransition

stateapproximately

determinedas_

k=(kQT/hyer^1^(same

caveataboutAGandAE)

E

Equilibriumand

Equilibriumconstantbetweentwominimarateconstants:

approximatelydeterminedasK=e*"nowweYe

(somesmallcareneededtouseAGtalkingreal

insteadofsE)

chemistry

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

值得思考的几个基本问题

很显然，势能面是一种有用的函数，那末对于一

个任意体系，我们如何来构筑它的势能面呢？

很多情况下不需要整个势能面，只需要势能面上

一些重要结构(MinimaandSaddlepoints)的能量,

那末，不通过构筑整个势能面，是否能够找到这

些重要的结构呢？

在不构筑整个势能面的情况下，我们怎样确定所

有重要结构的位置呢？这些重要结构又是如何相

关的呢？

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

势能面全貌自动搜索新方法

(GlobalReactionRouteMapping,GRRM)

----DevelopedbyOhno&Maeda

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

GlobalReactionRouteMapping(GRRM)

•Minimum(Equilibrium)andTS(TransitionState)are

extremalsonthePES

•GRRMcanbemadebyfine-tooth-combtestsof

mathematicalconditionatallpointsonPES

Asystemwith5atoms(9degreeoffreedom)

1009=1018

J

Ittakesmorethan30,000,000,000years!!

Therehadbeennoglobalreactionroutemapfor

systemscomposedofmorethan4atoms

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

GRRM万法的原理

Whenchemicalbondsdissociateor

reorganizeviaaTSleadingtoEQ,the

AnharmonicDownwardDistortion

(ADD)shouldhappenonthepotential

energysurface.

ThemaximaldirectionofADDisa

signpostofthechemicalreaction.

令Equilibrium:EQ(Minimum)

♦TransitionState:TS

HarmonicAnharmonic

')DalianUniversity

JofTechnologyGraduateCourse,Lecture52010Autumn

AnharmonicDownwardDistortion(ADD)

非简谐向下形变

化学键的断裂

导致离解反应

化学键的重排经过

一过渡态(TS)生成

新物质

(Equilibriumstructure)

DalianUniversity

yofTechnologyGraduateCourse,Lecture52010Autumn

AQuantumPrincipleofChemical

ReactionsforFindingaReactionRoute

•asignofadissociationchannelcanbedetectedasan

anharmonicdownwarddistortion(ADD).

•asignofachemicalreactionleadingtoanotherEQcan

bedetectedasanADD.

}DalianUniversity

JofTechnologyGraduateCourse,Lecture52010Autumn

GRRM方法的原理（续）

FordetectingADDaroundaEQ

IntroduceScaledNormalCoordinatetothe

iso-energyhypersurfaceofharmonicpotential(hyperelipsoide)

7/=41/2Qi

Theiso-energysurfacebecomessimplehypersphere

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

GRRM法工作的简单原理

StartfromanEQ

Repeat

Findallreactionroutes

uphillUwalking

DissociationTransition

Channel(DC)Structure(TS)

downhillwalki1ng

DissociationEquilibrium

Channel(DC)Structure(EQ)

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

关于GRRM方法的参考文献

Ohno,K.;Maeda,S.Chem.Phys.Lett.2004,384,277.

Maeda,S.;Ohno,K.J.Phys.Chem.A2005,109,5742.

Ohno,K.;Maeda,S.J.Phys.Chem.A2006,110,8933.

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

GRRM方法的应用

Case1:

Dialkyldithiophosphoratecuprous[Cu(I)]

Dissociationandisomerizationof

CuDDPanditsreactionwithCH3OO,.、H—Os

CuDDPisanengineoiladditive/PX/Cu

(antioxidationandantiware)H—OS

CuDDPamodelofCuDDP

Case2:

Titanocene-catalyzeddehydrocoupling3"^Me2N-BH2

2Me2NH-BH3

ofMe2NH-BH3-2唉H2B—NMe2

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

Case1

e

ReactionofCuDDPwithCH3OO

andCHoOOH

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

A

Oxidationofengine-oilandantioxidationofCuDDP

Oxidation:

Initiation

RH——，R-

Chain-reaction

R?+O2——ROO*(fast)(1)

ROO?+RH------'ROOH+R-(2)useantioxidantsto

undesirableduetocorrosiondecomposetheROO*

Antioxidation

Chain-termination(Peroxy-radicalscavenging)

Cu++ROO*------►Non-radicalproduct⑶

Cu++ROO«=RO-

oraligand-radicalforabstractingHfromROOH(4)

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

jE----------------------------------a

PreviousstudiesonCuDDP

Jf

Previousstudies

Onlyexperimentalstudiesonitssynthesisandapplication

Nocomputationalstudyfound

Knowledgeremainspoorlyunderstood:

EngineParts

EngineParts

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

CUDDP-OOCH3complex

c---------------------------------------(Energyinkcal/mol)------------------------------------------►

bond-rearrangementisomerizationperoxyl-radicaldecomposition

DalianUniversity

ofTechnologyG「aq椀息巡「游A(ecture52010Autumn

(OH)2PS2Cu-assistedCH3OOHdecomposition

(、TS[1-9]

lTS[3-4]\20.2TS[6-7]

a13.0\(10.0)13.2

F(1.0)(4.4)

a

TS[2-3]；

4.2；

TS[5-6]

(-6.9)ITS[1-2]\

0.2C影

It-0.91(-10.0)

H、(-11⑼

02

S1\\(-14.6)/z0.0[pCu—02

S2Z

/2(0.0)k

H

/Cu\，3-2.05

队-2.7

S2‘CH(-12.0)、H-4.5

3(-13.0)

(-14.4)-6.2

(-15.5)

01

TS[7-8]

.01.CH3-19.9

H，,，，

S1z(-31.8)

\/CH3[P][S：cuf

[P]02

、S2—CuS2O2f

4：

-31.2；

-24.2

(-41.7)；

(-36.0)

9：S1CH3!8

S1——Cu—02-''H：-69.4

-68.8!队/Cu、

H(-77.3)/：(-78.3)

HS202H2c21、

__：，、、H

H

俨%2/芦晟[P]=(HO)2P、/S1、，

A

HomolysisHeterolysis

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

InsightsfromGRRMcalculation

[P][〉Cu[[P]=(HOOP：CH3

Computationssuggestthat(OH)2PS2Cu(I)-mediated

decompositionofCH3OOHleadstoformaldehydeandwater

moleculesvia0-0bondheterolysisandsubsequentintramolecular

hydrogentransfer,withretainmentofthecopper(I)complex.

DalianUniversity

ofTechnologyGraduateCourse,Lecture52010Autumn

Case2

Titanocene-catalyzed

dehydrocouplingofMe2NH-BH3

DalianUniversity

ofTechnologyGradu