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云计算-分子、团簇和凝聚体系中相互作用的计算研究.pdf
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云计算-分子、团簇和凝聚体系中相互作用的计算研究.pdf
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lll
发现一种和实验观测到的2×2品格sTM图象符合得很好.以顶点和双键
接触衬底的两种1×l极小之间如果形成畴界,其畴界能为负值,这一点
也与实验观测的畴界的sTM图象符合.最后,我们探讨了构造更精确的
分子间势模型以及应用到一维c60体系中的可能性.J
Ab8tract
V
Along
with
the
rapid
progress
of
the
computational
methods
and
cor—jtio瑚,com-
putational
chemistry
and
computational
pllysics,which
are
aInong
the
most
important
developing
directioIls
of
chemistry
and
physic8,will
become more
and
more
crucial.Fbr
chemist8,the
m01ecul鹊and
the
chemical
bond8
are
the
b捆ic
patterIIs
to
understand
the
world.Between
the
aggregated
molecul髓,there
may
eXi8t
the
8trcng
meracti0砒of
chemical
bonding
or
the
nonbondingⅥ煳k
interactio瑚.The
computational
inve8tigatioIl8
for
the
three
kind8
of
iI址eractio璐(tl地iT吐ramolecular
chem沁a1
bondB,the
iIlterm01ecular
chemical
bonds,aIld
the
intermoleclllar
weak
interactio瑚)compose
the
thr∞part8
of
thi8
di88ertation.
In
Ghapter
l,we
brie丑y
introduce
the
quantum
cll咖is田alld
the
de珊ity胁ctional
theory(DFT)鹊、^,ell鹅the口b
ini“。softw缸e
padcage
Gau88iaIl
and
DM01,wllich
are
ollr
theoretical
foundatiolls
aIld
computation虹impl哪ent8
to
deal
with
the
intramoleclllar
and
interm01ecular
chemical
bond8.
In
Chapter
2,we
8tudied
the
cl璐ter8
alld
the
molecul朗u8ing
DFT.Since
the
d讳
covery
of
C60
clu8ter
in
1985,the
carbon-b勰is
c1118te瑁,with
the
mUerene8
a8
their
repre-
8entatives,h
a_ve
attracted
extensive
inter晒t8.Thu8
a
novel
6eld
of
clIemi¥try
and
material
science8
w鹪ori西nated.The
experimental
fabrication
of
the
C36
cry8t81
in
1998
turned
the嘲earch
inte嘟ts
from
C60
and
the
1arger
fulleren船to
the
8maller“lerene8.Our
cal-
culations
8howed
that址【ere
are
twO
kind8
of
isoenergetic
geometrie8
of
the
C36
molecule8,
i.e.,D材and
D6^.7黜ing
ad啪tage
of
the
calculatio璐for
the
catio璐and
aIlioIls
of
the
two
geometrie8,、糟g纠ve
a
1ikely
ex讲aIlation
for
the
experimental
D6^8ymmetry
of
the
C36
m01ecul朗in
me
s01ids,and
predicated
the
probability
of
producillg
the
D2d
i80mer.
The
metallocabonhederene8(met-cars)discovered
in
1992
are
another
kinds
of
e8pecially
stable
clusters.After
lon酽term
controver8y
aIld
resear血,the
m08t
stable
geometry
of
the
met—car8
have
been
found
as
not
like
fmlenrene,but
tetraeapped
tetrahedron
with
the
Td
symmetrF
We
calculated
the
electric
polarizabiliti朗of
a
8eri朗of
Td^如C12
met—cars.
The
molecular
8pectroscopy
is
the
most
traditional
research
project
of
our
1aborator弘
A10ng
wi曲the
progr鹊8
of
the
experimental
and
computationa】conditions,七he
researcll
about
the
band
inteIl8itie8
will
be
more
aIld
more
important.
The
vabrational
8pectro-
scopic
inteIlsitie8
are
determined
by
the
dipole
moment
surf如e(DMs)and
the
vibrational
wavefunctioll8,and
the
DMS
i8
more
important
betw∞n
the
two
term8.We
calculated
the
DMs
of
the
xH4
(x=si,Ge)aIld
CHY3(Y=cl,B
r'I)molecul鹪,and
investigated
the
Vibrational
inte瑚ities
usiI塔the
calclllated
DMS.
In
Chapter
3,we
turned
to
the
cllemisorbed
m01eclll朗.
In
virtue
of
it8
power“
abnities
of
sin—e
m01ecule
ima酉ng
and
maIlipulation,the
8calllling
tunneling
microscope
(sTM)has
greatly
impul8ed
the
bond
8elective
cllemi8try’the
surf乱e
science,and
the
single
molecule
cllemi8try
and
phy8ic8.Ⅵa
the
combination
of
the
STM
and
the
inel船tic
electronjc
tuIlILelin98pectroscopy(IETs),wilson
Ho
et耐.r娓lized
tIIe
me嬲urement8
ofthe
sill91e
molecule
vibration
frequenci鹊and
the
fo呻ation
of8ingle
chemical
bond.In
order
to
study
the
10cal
propertie8
of
the
adBorbate
molecul鹪,we
modeled
the
ad80rption
8ystem8
勰c1118ter,calculated
the
energie8
aIld
geometrie8瑚illg
DFT,aIld
siInlllated
the
STM
images.E8pecially
meaIdngfullyl
Via
co璐tructing
the
dyn砌c
matric髑of
the
ad80rbate
molecules,we
obtaiⅫed
the
relatively
accruate&equencies
of
the
intenIal
and
e】【ternal
modes,such
as
8tretcll,beⅡdin岛f}璐trated
rotation,and
fru8trated
traIl8latjon.
The
c出c、n乱ed
frequenc弛n眦only雄;r∞wioh
the删a_ble
exper细撒出蛆矾du鹧,but
ako
predict
maIly
mod鸽not
experiInentally
observed
yet.
Our
iIIve8tigation
fbr朋IcO)n
(M=Fe,co,Nl,cu,zn,and
AgI
n=1,2)on
Ag(110)8howed
that
the
6
metalB
can
be
80rted
to
two
cla8se8,eacll
of
whjch
exhibits
a
set
of
special
geometri船and
frequenci船,according
to
whether
its
d
orbital8
are
fully
occupied.The
adsorbate
geometries
caIl
be
lulde瑁tood
in
the
1ight
of
the
frontier
orbital
tlleory(FOT).Our
inV翩t培ation
for
actylene
aIld
it8
evolution
product8
on
Ag(110)showed
tllat
the
thermal
evolution
product
of
acetylene
di8covered
in
the
previous
HREELS
e】【periment
is
not
CCH,whicll
w捆跚igned
by
the
author8
then,but
CCH2.
Thi8
new勰s培I皿ent
w拍concluded
maillly
Via
compari80n
between
the
experimental
aIld
calculated
Vibrational
f}equencie8.
In
the
colIr8e
of
the
鹪8ignme呲,Ⅵ陀obta沁d
the
ad80rbate
orientation
0f
CCH2,whidl
w够not
indicated
by
experiments.
In
Chapter
4,we
studied
a
novel
phenomenon
typically
determined
by
nLe
inter.
●
牛
moleclllar
weak
interaction8,i.e.,the
orieⅡtational
domain
structure
of
the
tw0_dlme瑚iOnal
C60
8y8tem.At
260
K,the
three-dime珊ional
C60
solids
undergo
a
structural
6r8t·order
pha8e
traJl8ition
from
fcc
to
sc
structllre
which
is
tri鸥ered
by
the
orientRtional
ordering
of
the
C60
m01ecules.The
structure
researcll
1aboratory
at
USTC
f01llld
that
there
i8
a180
ori-
enta^bn“orderiI堰tran8ition
of
the
two-diIne璐ional
C60
ad80rbed
on
the
tMol
8ubstrate.
F0r
the
interest
of
explain
and
predict
the
experimental
phenomonon,、怕emplo”d
two
kinds
of
8emi-empirical
intermolecular
potential
model8
to
investigate
the
ordered
orienta-
tional
domain
8tructllr鹤of
the
tw沪dimeIlsional
C∞,includiIlg
the l×l
1attic朗,the
2×2
1attices,aIld
the
domajn
boundary
energi锚betljlreen
tw0
l【ind8
ofl×llattices.The嘟111t8
by
the
LM
model,which
is
the
more
re6nedt
Were
satisf如tory.Wb
follIId
that
under
the
limitation
of
the
1×1
lattice,there
are
three
kind宕of
orientatiolls
correspondiIlg
the
local
minima
on
the
orieInational
poten乞ial
energy
8urface.A眦mged
owing
to
their
8tabili瓴
the
three
kind8
of
orientatio璐contact
with
the
sub8trate瑚pectively
by
a
vert麟,a
dou-
ble
bond,and
a
hexagon.The
vertex—coHtacting
orientation
agre嘲rather
accurately
with
the
orientation
concluded
via
comparison
betw∞n
the
e】(perimental
alld
simulated
STM
images.Rela)【ing
the
periodic
boundary
to
the
2×2
lattice'the
f0眦er
tw0
kinds
ofl×l
orientatioIl8
keep
10cal
minimalbut
the
l鞠t
one
becom朗di8torted.Several
kind8
of
2×2
local
minima
orientatio瑚other
than
the
1×1
orientatio瑚were
found,but
their
energies
are“l
high艘than
that
0f
vertex-contacting
1×1
millima,which
i8
comi8tent
with
the
experimental
f如t
that
the
most
STM
images
are
of
the
l×l
1attic鹤.We
found
a
kind
of
2×2
orientation
other
than
the
l×l
0rientation
agree8
well
with
experimental
2×2
STM
image.The
domain
boundary
energy
between
the
vertex-contactiIlg
aIld恤e
double_bond—
contacting
l×l
orientation8
i8
negative,whicll
i8
accordant
wi七h
the
experimental
STM
image
of
the
domain
boundary.Finallyl
we
disc瑚8ed
the
p08sibili时of
co瑚tructing
more
precise
intermolecular
potenti出and
extending
the
re8earcll
to
on争dimen8ional
C60.
前
言
从1q世纪的经典化学到20世纪的现代化学的飞跃,从本质上来说,
是从19世纪的原子论、元素周期表等在原子的层次上定性、经验地认识
和研究化学,进步到20世纪在分子的层次上定量、基于物理原理地认
识和研究化学.这些进步表现在诸如对化学键的本质、分子间的强相互
作用和弱相互作用、材料的结构和性能的关系的认识,分子生物学的创
立,以及上千万种新化合物的合成等等.
量子化学家把20世纪物理学的伟大发现量子力学应用到分子体系
中,对化学键的本质获得了深刻的理解.以1927年氢分子结构的量子力
学理论作为开端,量子化学已经有了70多年的发展历史.至今已有6位
化学家因为量子化学和计算化学方面的贡献被授予了4届N0bel化学奖.
传统的第一性原理计算方法是基于单电子近似求解H”t盼Fock方程.但
是,Hartree-F0ck方程没有包括电子之间的相关效应,使其准确度受到内
在的限制.量子化学家发展了若干种考虑电子相关地求解电子波函数的
方法,如组态相互作用、耦合团簇理论等.这些方法的共同缺点在于计
算量随基函数数量的增长过快,以至难以扩展到较大的体系.幸好,电
子密度泛函理论(DFT)根据一条简单而深刻的定理,以电子密度而不
是波函数作为基本变量,提出了全新的思路.目前,密度泛函理论是最
流行的计算化学方法.计算化学在20世纪最后10年中获得了突飞猛进的
进展,并代表了化学未来发展的主要方向之一.
分子间强相互作用的代表性体系是共价固体和表面化学吸附.在固
体和表面中寻找化学成键,对于化学家是很自然的.从化学成键的观点
看来,固体中的离域键合与共轭体系分子类似,能带是由单体的分子轨
道交叠形成的,其宽度依赖于交叠的程度,而走向取决于轨道的拓扑性
质.当能带充满时,通过Bloch离域波函数的线性组合,可以得到wannier
函数的定域图象.对于部分填充的能带,只能采用离域的图象.为了分
析离域轨道中的成键,化学家可以使用态密度(DOs)和晶体轨道重叠
布居(c00P)等工具,以获得实空间轨道相互作用的图象.只需注意到
表面的轨道具有能带的连续结构,前线轨道理论即可自然地推广到表面
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