Molcas Forum

shuoshuo

Member

From: Beijing Normal University

Registered: 2017-10-18

Posts: 35

openmolcas+tinker QMMM-SCALE and CASROOT keywords usage

Dear Molcas experts，

I try to do qmmm calculations. I am exploring the QMMM  interface code of openmolcas and tinker. I find QMMM-SCALE and CASROOT keywords in the code file qmmmsetup.f
When I calculate excited-states, should I use CASROOT keyword, what value should I use of QMMM-SCALE?

c
c     Is there any QM/MM scale factor ?
c
         else if (keyword(1:11) .eq. 'QMMM-SCALE ') then
            read(string,*,err=10,end=10) qmmmscale,casroot
10          if (casroot .gt. 0) then
               write (iout,11) qmmmscale,casroot
11             format(/,' Initial QM/MM scale factor:' ,f7.3,
     &             ' for QM state ',i2)
            else if (casroot .lt. 0) then
               write (iout,12) qmmmscale,abs(casroot)
12             format(/,' Constant QM/MM scale factor: ',f7.3,
     &             ' for QM state ',i2)
            else
               write (iout,13) qmmmscale
13             format(/,' Constant QM/MM scale factor: ',f7.3)
            end if
            if (qmmmscale .le. 0.0d0) call fatal
         end if

niko

Member

From: Marseille

Registered: 2015-11-08

Posts: 59

Website

Re: openmolcas+tinker QMMM-SCALE and CASROOT keywords usage

Hi,
This keyword has been introduced for a very specific purpose: scaling the casscf energy and gradient to approximate the corresponding caspt2 values, as originally proposed in PNAS 104 (2007) 7764. I won't recommend using this keyword, unless you already map casscf and caspt2 energy surfaces along your reaction coordinate(s).

shuoshuo

Member

From: Beijing Normal University

Registered: 2017-10-18

Posts: 35

Re: openmolcas+tinker QMMM-SCALE and CASROOT keywords usage

Thank you !