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Part 2<br />

Atomic Orbital Based Response Theory<br />

The first term is simply the geometrical gradient of the ground state. In ref. 66 this was shown to be<br />

E<br />

0 x = 2Tr x + Tr x ( ) + Tr<br />

x + hnuc<br />

x<br />

Dh DG D D F . (2.103)<br />

The other terms are found as the derivative of the matrix expressions in Eq. (2.91) and (2.92)<br />

f † [2]<br />

∂b E b<br />

∂x<br />

f † [2]<br />

f<br />

f<br />

( ( ))<br />

=− Tr F + G D ⎡ , , ⎤ −Tr ⎡ , , ⎤<br />

⎣<br />

b D b<br />

⎦<br />

F<br />

⎣<br />

b D b<br />

⎦<br />

x x f f † f x f †<br />

⎡⎣ ⎤⎦ ⎡ ⎤<br />

S S ⎣ ⎦S<br />

−Tr F⎡⎡⎣ , ⎤⎦ x<br />

, ⎤ Tr ⎡⎡ ⎣ , ⎤⎦<br />

, ⎤<br />

⎣<br />

b D b<br />

⎦<br />

F<br />

⎣<br />

b D b<br />

⎦<br />

f f † f f †<br />

−<br />

S S<br />

S<br />

†<br />

( ⎡ ⎤ ) ⎡ ⎤<br />

S<br />

S<br />

f x f † f †<br />

( ⎡ ⎤ )( ⎡ ⎤ ⎡ ⎤<br />

x )<br />

x f f<br />

− Tr G ⎣b , D⎦ ⎣D,<br />

b ⎦<br />

− 2Tr G ⎣b , D⎦ ⎣D , b ⎦ + ⎣D,<br />

b ⎦<br />

∂b S b<br />

f † x f<br />

− ω<br />

= −ωTr b S ⎡ , ⎤<br />

∂x<br />

⎣D b ⎦ S<br />

S<br />

S S S<br />

( ⎡ ⎤ ⎡ ⎤<br />

x<br />

⎡ ⎤ )<br />

f † x f f f x<br />

⎣ ⎦S ⎣ ⎦S ⎣ ⎦S<br />

− ω Tr b S D , b S+ D, b S+<br />

D,<br />

b S<br />

S<br />

x<br />

S<br />

(2.104)<br />

(2.105)<br />

∂( FDS −SDF<br />

)<br />

x x x x A<br />

− X = − 2X⎡<br />

+ ( ) + + ⎤<br />

∂x<br />

⎣F DS G D DS FD S FDS ⎦ , (2.106)<br />

where F x = h x + G x (D). Collecting the various terms we obtain<br />

f<br />

∂E<br />

∂x<br />

f f † x f † x f<br />

( D ⎡<br />

⎤<br />

⎣<br />

⎡⎣b D⎤⎦ b [ ]<br />

S ⎦<br />

D X<br />

S ) h ⎡ ⎤<br />

S<br />

( ⎡ ⎤<br />

S<br />

)<br />

S<br />

⎣D b ⎦ G ⎣b D⎦<br />

f f †<br />

x x<br />

( D ⎡⎡<br />

⎣b D⎤⎦<br />

b ⎤ [ D X]<br />

) G D hnuc<br />

= Tr 2 − , , − , −Tr , ,<br />

+ Tr −<br />

⎣<br />

, ,<br />

⎦<br />

− , ( ) +<br />

S<br />

S<br />

S<br />

x f f † x f † f †<br />

f<br />

DG( ⎡<br />

⎤<br />

⎣<br />

⎡⎣b D⎤⎦ b ) ( x<br />

S ⎦<br />

⎡<br />

S S<br />

) (<br />

S<br />

)<br />

S ⎣D b ⎤⎦ ⎡⎣Db ⎤⎦ G ⎡⎣b D⎤⎦<br />

x<br />

x<br />

DG( [ DX]<br />

) ( ⎡ ⎤ [ ] x<br />

S ⎣D X⎦<br />

DX<br />

S<br />

S<br />

) F<br />

f x<br />

( ⎡<br />

f † † †<br />

⎡⎣<br />

b D ⎤ , ⎤ ⎡<br />

f f<br />

,<br />

x<br />

, ⎤ ⎡<br />

f f<br />

, , ⎤<br />

⎣ ⎦ b<br />

S ⎦<br />

+<br />

S S<br />

x )<br />

S ⎣⎣ ⎡b D⎦⎤ b<br />

⎦<br />

+<br />

S ⎣⎣ ⎡b D⎦⎤<br />

b<br />

⎦<br />

F<br />

S<br />

f † f x f f x<br />

Tr b S( ⎡b , D ⎤ S ⎡b , D⎤ x<br />

S ⎡b , D⎤<br />

S )<br />

−Tr , , − 2Tr , + , ,<br />

−Tr , − Tr , + ,<br />

− Tr ,<br />

+ ω f ⎣ ⎦ + ⎣ ⎦ + ⎣ ⎦<br />

f † x f<br />

+ ω f Tr b S ⎡⎣b , D⎤⎦<br />

S,<br />

G b D b , ( [ , ] )<br />

where ( ⎡<br />

f<br />

f †<br />

, , ⎤<br />

⎣<br />

⎡⎣<br />

⎤⎦S<br />

⎦ )<br />

S<br />

G x x f<br />

(D), ( ⎡ , ⎤ )<br />

S<br />

S S S<br />

f<br />

G D X , ( ⎡ , ⎤ )<br />

(2.107)<br />

G S ⎣ b D ⎦ and F can be evaluated, whereas<br />

S<br />

G ⎣ b D ⎦ , h x and nuc<br />

x<br />

h have to be evaluated for each geometrical perturbation.<br />

S<br />

Note that no two-electron integrals are represented explicitly, in order to obtain the best<br />

performance – e.g. for linear scaling codes - no reference should be made to four-index integrals.<br />

2.4.4 The First-order Excited State Properties<br />

The expression for the first-order one-electron excited state properties for perturbation independent<br />

basis sets is obtained from the expression for the excited state gradient by omitting all two-electron<br />

derivative terms, as well as all terms involving the derivative of the overlap matrix<br />

74

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