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These methods are activated by setting the *$rem* keyword METHOD to
RICIS(D), SOSCIS(D), and SOSCIS(D0), respectively.
Other keywords are the same as in CIS method explained in
Section 7.2.1. As these methods rely on the RI approximation,
AUX_BASIS needs to be set by following the same guide as in RI-MP2
(Section 6.6).

METHOD

Excited state method of choice

TYPE:

STRING

DEFAULT:

None

OPTIONS:

RICIS(D)
Activate RI-CIS(D)
SOSCIS(D)
Activate SOS-CIS(D)
SOSCIS(D0)
Activate SOS-CIS(D${}_{0}$)

RECOMMENDATION:

None

CIS_N_ROOTS

Sets the number of excited state roots to find

TYPE:

INTEGER

DEFAULT:

0
Do not look for any excited states

OPTIONS:

$n$
$n>0$ Looks for $n$ excited states

RECOMMENDATION:

None

CIS_SINGLETS

Solve for singlet excited states (ignored for spin unrestricted systems)

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE
Solve for singlet states
FALSE
Do not solve for singlet states.

RECOMMENDATION:

None

CIS_TRIPLETS

Solve for triplet excited states (ignored for spin unrestricted systems)

TYPE:

LOGICAL

DEFAULT:

TRUE

OPTIONS:

TRUE
Solve for triplet states
FALSE
Do not solve for triplet states.

RECOMMENDATION:

None

SET_STATE_DERIV

Sets the excited state index for analytical gradient calculation
for geometry optimizations and vibrational analysis with SOS-CIS(D${}_{0}$)

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

$n$
Select the $n$th state.

RECOMMENDATION:

Check to see that the states do no change order during an optimization.
For closed-shell systems, either CIS_SINGLETS or CIS_TRIPLETS
must be set to false.

MEM_STATIC

Sets the memory for individual program modules

TYPE:

INTEGER

DEFAULT:

64
corresponding to 64 MB

OPTIONS:

$n$
User-defined number of megabytes.

RECOMMENDATION:

At least $150({N}^{2}+N)D$ of MEM_STATIC is required
($N$: number of basis functions, $D$: size of a double precision storage, usually 8).
Because a number of matrices with ${N}^{2}$ size also need to be
stored, 32–160 MB of additional MEM_STATIC is needed.

MEM_TOTAL

Sets the total memory available to Q-Chem

TYPE:

INTEGER

DEFAULT:

2000
2 GB

OPTIONS:

$n$
User-defined number of megabytes

RECOMMENDATION:

The minimum memory requirement of RI-CIS(D) is approximately
MEM_STATIC + max$(3SVXD,3{X}^{2}D)$
($S$: number of excited states, $X$: number of auxiliary basis
functions, $D$: size of a double precision storage, usually 8). However, because
RI-CIS(D) uses a batching scheme for efficient evaluations of electron
repulsion integrals, specifying more memory will significantly speed up the
calculation. Put as much memory as possible if you are not sure
what to use, but never put any more than what is available.
The minimum memory requirement of SOS-CIS(D) and SOS-CIS(D${}_{0}$) is approximately
MEM_STATIC + $20{X}^{2}D$. SOS-CIS(D${}_{0}$) gradient calculation
becomes more efficient when $30{X}^{2}D$ more memory space is given.
Like in RI-CIS(D), put as much memory as possible if you are not sure what to use.
The actual memory size used in these calculations will be printed out in the output file
to give a guide about the required memory.

SOS_FACTOR

Sets the scaling parameter ${c}_{T}$

TYPE:

INTEGER

DEFAULT:

1300000
corresponding to 1.30

OPTIONS:

$n$
${c}_{T}=n/1000000$

RECOMMENDATION:

Use the default

SOS_UFACTOR

Sets the scaling parameter ${c}_{U}$

TYPE:

INTEGER

DEFAULT:

151
For SOS-CIS(D), corresponding to 1.51
140
For SOS-CIS(D${}_{0}$), corresponding to 1.40

OPTIONS:

$n$
${c}_{U}=n/100$

RECOMMENDATION:

Use the default