4.2.51. SURFACEHOP

This module deals with surface hop semiclassical molecular dynamics (SHMD) and has to be used together with module DYNAMIX. Its purpose is the calculation of the relax root for the next step of the SHMD. In this moment the implemented algorithm under this module is the Tully’s fewest switches [195], along with the Hammes-Schiffer/Tully scheme [196] and the decoherence correction proposed by Granucci and Persico [197].

4.2.51.1. Output files

RUNFILE
Surface hop information such as Amatrix and CI coefficients for previous steps are stored in this file.

4.2.51.1.1. Input

&Gateway
coord=$Project.xyz
basis=6-31G*
group=nosym

>> FOREACH A in (1..400)

&Seward

&rasscf
 jobiph
 cirestart
 nactel = 6 0 0
 inactive = 23
 ras2 = 6
 ciroot = 2 2 1
 prwf = 0.0
 mdrlxroot = 2

&Surfacehop
 tully
 decoherence = 0.1
 psub

&alaska

&Dynamix
 velver
 dt = 41.3
 velo = 1
 thermo = 0
>>> End Do

4.2.51.2. General keywords

TULLY
This keyword enables the Tully–Hammes-Schiffer integration of the TDSE for the Tully Surface Hop Algorithm. If you use this keyword you should not use the HOP keyword in DYNAMIX.
DECOHERENCE
This keyword must be used after the TULLY keyword. It enables the decoherence correction in the population density matrix as reported by Persico–Granucci. The value is called decay factor and it is usually 0.1 hartree. It can be seen as how strongly this correction is applied. It is recommendable to leave it to 0.1, unless you really know what your’re doing.
SUBSTEP
This keyword must be used after the TULLY keyword. This keyword specifies how many steps of integration we use to interpolate/extrapolate between two Newton’s consecutive steps. The default is usually a good compromise between quickness and precision (200 substeps each femtoseconds of MD).
PSUB
This keyword must be used after the TULLY keyword. To print in Molcas output \(\mat{D}\) matrix, \(\mat{A}\) matrix, \(\mat{B}\) matrix, probabilities, randoms, population and energies at each substep (quite verbose, but gives you a lot of useful information).
DMTX
This keyword must be used after the TULLY keyword. With this keyword you can start your calculation with an initial \(\mat{A}\) matrix (population density matrix). It is a complex matrix. In the first line after the keyword you must specify its dimension \(N\). Then \(N\) lines (\(N\) values each line) with the real part of the matrix followed by \(N\) more lines with the imaginary part.
FRANDOM
This keyword must be used after the TULLY keyword. It fixes the random number to one provided by the user, in case a deterministic trajectory is needed
ISEED
This keyword must be used after the TULLY keyword. The initial seed number is read from the input file. Then, seed numbers are modified (in a deterministic way), saved in the RunFile and read in the next call to the module. This way, MD simulations are reproducible.
MAXHOP
This keyword must be used after the TULLY keyword. It specifies how many non-adiabatic transitions are allowed between electronic states.
H5RESTART
This keyword allows to restart a surface hopping trajectory calculation from an HDF5 file. The name of the restart file is given on the next line.

4.2.51.3. Input examples

This example shows an excited state CASSCF MD simulation of a methaniminium cation using the Tully Surface Hop algorithm. Within the SURFACEHOP module The keyword TULLY enables the TDSE integration. The options used in this case are: (SUBSTEP=200) to specify 200 substep of electronic integration between Newton’s, (DECOHERENCE=1) to deal with the decoherence using a decay constant of 0.1 hartree and (PSUB) to print the substeps matrices verbosely into the Molcas log.

&GATEWAY
 COORD
 6
 Angstrom
 C  0.00031448  0.00000000  0.04334060
 N  0.00062994  0.00000000  1.32317716
 H  0.92882820  0.00000000 -0.49115611
 H -0.92846597  0.00000000 -0.49069213
 H -0.85725321  0.00000000  1.86103989
 H  0.85877656  0.00000000  1.86062860
 BASIS= 3-21G
 GROUP= nosym

>> FOREACH ITER in (1 .. 1000)

&SEWARD

>> IF ( $ITER = 1 )

&RASSCF
  LUMORB
 FileOrb= $Project.GssOrb
 Symmetry= 1
 Spin= 1
 nActEl= 2 0 0
 Inactive= 7
 RAS2= 2
 CIroot= 3 3 1

>> COPY $Project.JobIph $Project.JobOld

>> ENDIF

&RASSCF
 JOBIPH; CIRESTART
 Symmetry= 1
 Spin= 1
 nActEl= 2 0 0
 Inactive= 7
 RAS2= 2
 CIroot= 3 3 1
 MDRLXR= 2

>> COPY $Project.JobIph $Project.JobOld

&surfacehop
 TULLY
 SUBSTEP = 200
 DECOHERENCE = 0.1
 PSUB

&ALASKA

&Dynamix
 VELVer
 DT= 10.0
 VELO= 3
 THER= 2
 TEMP=300

>> END DO