CCL:G: how to freeze in gaussian

 Sent to CCL by: "Sofia Vasilakaki" [svasilak%a%chem.uoa.gr]
 Hi,
 There are a few things you might want to try. Usually 'nosymm' keyword
 will keep the atoms fixed during opt. 'modredundant' usually works for me.
 There are some examples here http://www.gaussian.com/g_tech/g_ur/k_opt.htm
 (scroll down) in case you haven't seen them.
 Here http://www.ccl.net/chemistry/resources/messages/2004/06/02.007-dir/
 is an older thread.
 Cheers,
 Sofia V.
 >
 > Sent to CCL by: "kiran  k" [kd2f..mtmail.mtsu.edu]
 > Dear CCLusers,
 >
 > Could anyone suggest how to find interaction energy between formaldehyde
 > and
 > fluoride ion in gaussian using z-matrix, by keeping the distance constant.
 > After the calculation, the distance changed. Here is my example input look
 > like
 >  ----------------------------------------------------------------------
 > #P B3LYP/6-31+G* opt Test
 >
 > Geometry Optimization
 >
 > -1 1
 > C
 > O  1  r2
 > F  1  r3  2  a3
 > H  1  r4  2  a4  3  d4
 > H  1  r5  2  a5  3  d5
 > Variables:
 > r2= 1.2246
 > a3=  90.00
 > r4= 1.1017
 > a4= 122.24
 > d4= 354.18
 > r5= 1.1017
 > a5= 122.24
 > d5= 174.18
 > constant:
 > r3= 2.5000
 >
 > Thank you in advance>
 >
 >