<PAGE>

                                                                    Exhibit 10.5

--------------------------------------------------------------------------------




                            EQUITY PURCHASE AGREEMENT

                                     between

                               ICONIXX CORPORATION

                                       and

                          THAYER ITECH HOLDINGS, L.L.C.

                                       and

                                TC ITECH, L.L.C.






                              Dated March 22, 2000



--------------------------------------------------------------------------------
<PAGE>

LIST OF EXHIBITS
----------------
Exhibit A     Amended and Restated Certificate of Incorporation of Iconixx
              Corporation
Exhibit B     Capitalization Schedule

                                      -i-
<PAGE>

                              PURCHASE AGREEMENT
                              ------------------


     THIS AGREEMENT is made as of March 22, 2000, between ICONIXX CORPORATION, a
Delaware corporation (formerly, Empyrean Group Holdings, Inc.) (the "Company"),
THAYER ITECH HOLDINGS, L.L.C., a Delaware limited liability company ("Thayer
Holdings"), and each of the other persons or entities set forth in the Schedule
                                                                       --------
of Purchasers attached hereto (collectively with Thayer Holdings, the
-------------
"Purchasers" and individually a "Purchaser"). Except as otherwise indicated
herein, capitalized terms used herein are defined in Section 7 hereof.
                                                     ---------


                                   Recitals:
                                   --------

     At the Closing, the Purchasers desire to purchase from the Company, and the
Company desires to sell to the Purchasers (i) an aggregate of 16,100 shares of
the Company's Class A Preferred Stock, par value $.01 per share (the "Class A
Preferred") and (ii) an aggregate of 3,000,000 shares of the Company's Common
Stock, $.01 par value per share (the "Common"), in the amount set forth opposite
each Purchaser's name on the Schedule of Purchasers attached hereto.
                             ----------------------

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:



                                   ARTICLE I
                           AUTHORIZATION AND CLOSING
                           -------------------------

     1.1 Authorization of the Stock. The Company shall authorize the issuance
         --------------------------
and sale to the Purchasers of up to an aggregate of 16,100 shares of Class A
Preferred and an aggregate of 3,000,000 shares of Common, each having the rights
and preferences set forth in Exhibit A attached hereto. The Class A Preferred
                             ---------
and the Common are collectively referred to herein as the "Stock."

     1.2 Purchase and Sale of the Stock at Closing.
         -----------------------------------------

         (a) Purchase of Stock. Subject to the terms and conditions set forth in
             -----------------
this Section 1.2 and in Section 2.1, at the Closing, the Company shall sell to
     -----------        -----------
each Purchaser and, each Purchaser shall purchase from the Company:

             (i)   that number of shares of the Class A Preferred set forth
     opposite such Purchaser's name in the Schedule of Purchasers attached
                                           ----------------------
     hereto, at a purchase price of $1,000 per share; and
<PAGE>

             (ii)  that number of shares of the Common set forth opposite such
     Purchaser's name set forth in the Schedule of Purchasers attached hereto,
     at a purchase price of $1.30 per share.

         (b) Use of Proceeds of Purchase. The funds obtained by the Company from
             ---------------------------
the Purchasers at the Closing shall, together with debt financing provided by
First Union National Bank, N.A. and NationsBank, National Association pursuant
to the Credit Agreement dated August 12, 1999, as amended, between Lender, the
Company and its Subsidiaries, be used to (i) finance the Company's costs of
consummating the acquisitions of the assets of EnterpriseWorks, LLC and Internet
Information Systems, Inc. (the "Acquisitions") and (ii) provide funds for the
Company's working capital requirements.

         (c) Closing. The closing of the purchase and sale of the Stock to be
             -------
purchased pursuant to Sections 1.2(a) (the "Closing") shall take place at the
                      ---------------
offices of Hogan & Hartson, LLP, 555 Thirteenth Street, NW, Washington, D.C.,
20004 at 10:00 a.m. on March 23, 2000 or at such other place or on such other
date as may be mutually agreeable to the Company and the Purchasers. At the
Closing, the Company shall deliver to each Purchaser stock certificates
evidencing the Stock to be purchased by such Purchaser, registered in such
Purchaser's name, upon payment of the purchase price thereof by, at the
Company's option, either a cashier's or certified check, or by wire transfer of
immediately available funds to such account as designated by the Company.


                                   ARTICLE II
                    CONDITIONS OF THE PURCHASERS' OBLIGATIONS
                                   AT CLOSING

     2.1 Closing Conditions. The obligation of the Purchasers to purchase and
         ------------------
pay for the Stock at the Closing is subject to the satisfaction as of the
Closing of the following conditions:

         (a) Representations and Warranties, Covenants. The representations and
             -----------------------------------------
warranties contained in Section 5 hereof shall be true and correct at and as of
                        ---------
the Closing as though then made, except to the extent of changes caused by the
transactions expressly contemplated herein; and the Company shall have performed
in all material respects all of the covenants required to be performed by it
hereunder prior to the Closing.

         (b) Consummation of Acquisitions. The Company shall have entered into
             ----------------------------
at least one of the two definitive purchase agreements with respect to the
Acquisitions and such Acquisition Agreement(s) shall be in full force and effect
as of the Closing.

         (c) Compliance with Applicable Laws. The purchase of Stock by the
             -------------------------------
Purchasers hereunder shall not be prohibited by any applicable law or
governmental regulation, shall not subject the Purchasers to any penalty,
liability or, in the Purchasers' sole judgment, other onerous conditions under
or pursuant to any applicable law or governmental regulation, and

                                      -2-
<PAGE>

shall be permitted by laws and regulations of the jurisdictions to which the
Purchasers are subject.

         (d) Waiver. Any condition specified in this Section 2.1 may be waived
             ------
only if such waiver is set forth in a writing executed by the Purchasers.

         (e) Board Approval. The Board shall have approved the purchase of Stock
             --------------
by the Purchasers and the use of proceeds, including the consummation of the
Acquisitions.



                                  ARTICLE III
                                   COVENANTS
                                   ---------

     3.1 Intentionally Left Blank.
         ------------------------



                                  ARTICLE IV
                       TRANSFER OF RESTRICTED SECURITIES
                       ---------------------------------

     4.1 Transfer of Restricted Securities.
         ---------------------------------

         (a) Restricted Securities are transferable only pursuant to (i) public
offerings registered under the Securities Act, (ii) Rule 144 or Rule 144A of the
Securities Act (or any similar rule or rules then in force) if such rule or
rules are available and (iii) subject to the conditions specified in Section
                                                                     -------
4.1(b) below, any other legally available means of transfer.
------

         (b) In connection with the transfer of any Restricted Securities (other
than a transfer described in Section 4.1(a)(i) or (ii) above), the holder
                             -----------------    ----
thereof shall deliver written notice to the Company describing in reasonable
detail the transfer or proposed transfer, together with an opinion of Hogan &
Hartson LLP, or other counsel which (to the Company's reasonable satisfaction)
is knowledgeable in securities law matters to the effect that such transfer of
Restricted Securities may be effected without registration of such Restricted
Securities under the Securities Act. In addition, if the holder of the
Restricted Securities delivers to the Company an opinion of Hogan & Hartson LLP,
or such other counsel that no subsequent transfer of such Restricted Securities
shall require registration under the Securities Act, the Company shall promptly
upon such contemplated transfer deliver new certificates for such Restricted
Securities which do not bear a customary Securities Act legend. If the Company
is not required to deliver new certificates for such Restricted Securities not
bearing such legend, the holder thereof shall not transfer the same until the
prospective transferee has confirmed to the Company in writing its agreement to
be bound by the conditions contained in this Section 4.1 and Section 6.1.
                                             -----------     -----------

         (c) Upon the request of the Purchaser, the Company shall promptly
supply to the Purchasers or their respective prospective transferees all
information regarding the

                                      -3-
<PAGE>

Company required to be delivered in connection with a transfer pursuant to Rule
144A of the Securities Act.


                                   ARTICLE V
                 REPRESENTATIONS AND WARRANTIES OF THE COMPANY
                 ---------------------------------------------

     As a material inducement to the Purchasers to enter into this Agreement and
purchase the Stock, the Company hereby represents and warrants to the Purchasers
that:

     5.1 Organization and Corporate Power. The Company is a corporation duly
         --------------------------------
organized, validly existing and in good standing under the laws of the state of
Delaware and is qualified to do business in every jurisdiction in which the
failure to so qualify might reasonably be expected to have a material adverse
effect on the financial condition, operating results, assets, operations or
business prospects of the Company and its Subsidiaries taken as a whole. The
Company has all requisite corporate power and authority and all material
licenses, permits and authorizations necessary to own and operate its
properties, to carry on its businesses as now conducted and presently proposed
to be conducted and to carry out the transactions contemplated by this
Agreement.

     5.2 Capital Stock and Related Matters.
         ---------------------------------

         (a) As of the Closing and immediately thereafter, the authorized
capital stock of the Company shall consist of 100,000,000 shares of stock, of
which (i) 150,000 shares shall be designated as Class A Preferred and (ii)
99,850,000 shares shall be designated as Common Stock. The issued and
outstanding Class A Preferred Stock and the Common Stock are as set forth on
Exhibit B hereto. As of the Closing, all of the outstanding shares of the
---------
Company's capital stock shall be validly issued, fully paid and nonassessable.

         (b) Based in part on the investment representations of the Purchasers
in Section 6.1 hereof, the offer, sale and issuance of Stock hereunder does not
and will not require registration under the Securities Act or any applicable
state securities laws.

     5.3 Authorization; No Breach. The execution, delivery and performance of
         ------------------------
this Agreement and all other agreements contemplated hereby to which the Company
is a party have been duly authorized by the Company. This Agreement and all
other agreements contemplated hereby each constitutes a valid and binding
obligation of the Company, enforceable in accordance with its terms. The
execution and delivery by the Company of this Agreement and all other agreements
contemplated hereby to which the Company is a party, the offering, sale and
issuance of the Stock hereunder and pursuant to Section 1.2(a), the Amended and
                                                --------------
Restated Certificate of Incorporation and the fulfillment of and compliance with
the respective terms hereof and thereof by the Company do not and will not (i)
conflict with or result in a breach of the terms, conditions or provisions of,
(ii) constitute a default under, (iii) result in the creation of any lien,
security interest, charge or encumbrance upon the Company's capital stock or
assets pursuant to, (iv) give any third party the right to modify, terminate or
accelerate any obligation under, (v) result in a violation of, or (vi) require
any authorization, consent, approval, exemption

                                      -4-
<PAGE>

or other action by or notice to any court or administrative or governmental body
pursuant to, the Certificate of Incorporation or bylaws of the Company, or any
law, statute, rule or regulation to which the Company is subject, or any
agreement, instrument, order, judgment or decree to which the Company is a party
or by which it is bound.

     5.4 Violations of Laws. The Company has not (i) violated any laws or
         ------------------
governmental rules or regulations, which violation would reasonably be expected
to have a material adverse effect upon the financial condition, operating
results, assets, operations or business prospects of the Company; (ii) received
notice of any such material violation; or (iii) become subject to any material
clean up liability, and the Company has no reason to believe it may become
subject to any material clean up liability, under any federal, state or local
environmental law, rule or regulation.

     5.5 Governmental Consent, etc. Except for approvals under the HSR Act, no
         -------------------------
material permit, consent, approval or authorization of, or declaration to or
filing with, any governmental authority is required in connection with the
execution, delivery and performance by the Company of this Agreement or the
other agreements contemplated hereby, or the consummation by the Company of any
other transactions contemplated hereby or thereby including the Acquisitions.

     5.6 Disclosure. Neither this Agreement nor any of the schedules,
         ----------
attachments, written statements, documents, certificates or other items prepared
or supplied to the Purchasers by or on behalf of the Company with respect to the
transactions contemplated hereby contain any untrue statement of a material fact
or omit a material fact necessary to make each statement contained herein or
therein not misleading. There is no fact which the Company has not disclosed to
the Purchasers in writing and of which any of its officers, directors or
executive employees is aware and which has had or might reasonably be
anticipated to have a material adverse effect upon the existing or expected
financial condition, operating results, assets, customer or supplier relations,
employee relations or business prospects of the Company.



                                  ARTICLE VI
                   PURCHASERS REPRESENTATIONS AND WARRANTIES
                   -----------------------------------------

     As a material inducement to the Company to enter into this Agreement, each
Purchaser hereby represents and warrants to the Company, with respect to itself
and not jointly, as follows:

     6.1 Purchaser's Investment Representations. Such Purchaser (i) is acquiring
         --------------------------------------
the Restricted Securities purchased hereunder or acquired pursuant hereto for
its own account with the present intention of holding such securities for
purposes of investment, (ii) has no intention of selling such securities in a
public distribution in violation of the federal securities laws or any
applicable state securities laws and (iii) is an "accredited investor" as
defined in the Securities Act; provided that nothing contained herein shall
prevent such Purchaser and subsequent holders of Restricted Securities from
transferring such securities in compliance with

                                      -5-
<PAGE>

the provisions of Article IV hereof. Each certificate for Restricted Securities
                  ----------
shall be imprinted with a customary securities legend in a form provided by the
Company's counsel.

     6.2 Authorization; No Breach. The execution, delivery and performance of
         ------------------------
this Agreement and all other agreements contemplated hereby to which such
Purchaser is a party have been duly authorized by such Purchaser. This Agreement
and all other agreements contemplated hereby to which a Purchaser is a party
each constitutes a valid and binding obligation of such Purchaser, enforceable
in accordance with its terms. The execution and delivery by such Purchaser of
this Agreement, the Stockholders Agreement and all other agreements contemplated
hereby to which such Purchaser is a party, and compliance with the respective
terms hereof and thereof by such Purchaser do not and will not (i) conflict with
or result in a breach of the terms, conditions or provisions of, (ii) constitute
a default under, (iii) result in the creation of any lien, security interest,
charge or encumbrance upon such Purchaser's capital stock or assets pursuant to,
(iv) give any third party the right to modify, terminate or accelerate any
obligation under, (v) result in a violation of, or (vi) require any
authorization, consent, approval, exemption or other action by or notice to any
court or administrative or governmental body pursuant to, the charter or
organizational documents of such Purchaser, if applicable, or any law, statute,
rule or regulation to which such Purchaser is subject, or any agreement,
instrument, order, judgment or decree to which such Purchaser is a party or by
which it is bound.



                                  ARTICLE VII
                                  DEFINITIONS
                                  -----------


     For the purposes of this Agreement, the following terms have the meanings
set forth below:

     "Affiliate" of any particular person or entity means any other person or
entity controlling, controlled by or under common control with such particular
person or entity.

     "Class A Preferred" has the meaning set forth in the Recitals to this
Agreement.

     "Certificate of Incorporation" means the Company's amended and restated
Certificate of Incorporation filed with the Secretary of State of the State of
Delaware on August 12, 1999.

     "Closing" has the meaning set forth in Section 1.2(c).
                                            --------------

     "Common" has the meaning set forth in Recitals to this Agreement.

     "Common Stock" means collectively, the Common and any other class of the
Company's common stock, $.01 par value per share.

                                      -6-
<PAGE>

     "Indebtedness" means all indebtedness for borrowed money (including
purchase money obligations), all indebtedness under revolving credit
arrangements, all capitalized lease obligations and all guarantees of any of the
foregoing.

     "Investor Common" means (i) the Common Stock issued hereunder and (ii) any
Common Stock issued or issuable with respect to the Common Stock referred to in
clause (i) above by way of stock dividends or stock splits or in connection with
a combination of shares, recapitalization, merger, consolidation or other
reorganization. As to any particular shares of Investor Common, such shares
shall cease to be Investor Common when they have been (a) effectively registered
under the Securities Act and disposed of in accordance with the registration
statement covering, them or (b) distributed to the public through a broker,
dealer or market maker pursuant to Rule 144 under the Securities Act (or any
similar rule then in force).

     "Investor Preferred" means (i) the Class A Preferred issued hereunder and
(ii) any Class A Preferred issued or issuable with respect to the Class A
Preferred referred to in clause (i) above by way of stock dividends or stock
splits or in connection with a combination of shares, recapitalization, merger,
consolidation or other reorganization. As to any particular shares of Investor
Preferred, such shares shall cease to be Investor Preferred when they have been
(a) effectively registered under the Securities Act and disposed of in
accordance with the registration statement covering them, (b) distributed to the
public through a broker, dealer or market maker pursuant to Rule 144 under the
Securities Act (or any similar rule then in force) or (c) redeemed by the
Company.

     "Investor Stock" means the Investor Preferred and the Investor Common.

     "Person" means an individual, a partnership, a limited liability company, a
corporation, an association, a joint stock company, a trust, a joint venture, an
unincorporated organization and a governmental entity or any department, agency
or political subdivision thereof.

     "Restricted Securities" means (i) the Stock issued hereunder and (ii) any
securities issued with respect to the securities referred to in clause (i) above
by way of a stock dividend or stock split or in connection with a combination of
shares, recapitalization, merger, consolidation or other reorganization. As to
any particular Restricted Securities, such securities shall cease to be
Restricted Securities when they have (A) been effectively registered under the
Securities Act and disposed of in accordance with the registration statement
covering them, (B) become eligible for sale pursuant to Rule 144(k) (or any
similar provision then in force) under the Securities Act or (C) been otherwise
transferred and new certificates for them not bearing a customary Securities Act
legend have been delivered by the Company in accordance with Section 4.1(b).
                                                             --------------
Whenever any particular securities cease to be Restricted Securities, the holder
thereof shall be entitled to receive from the Company, without expense, new
securities of like tenor not bearing a customary Securities Act legend.

     "Securities Act" means the Securities Act of 1933, as amended, or any
similar federal law then in force.

                                      -7-
<PAGE>

     "Securities Exchange Act" means the Securities Exchange Act of 1934, as
amended, or any similar federal law then in force.

     "Securities and Exchange Commission" includes any governmental body or
agency succeeding to the functions thereof.

     "Stock" has the meaning set forth in Section 1.1 of this Agreement.
                                          -----------

     "Subsidiary" means any corporation of which the securities having a
majority of the ordinary voting power in electing the board of directors or
otherwise are, at the time as of which any determination is being made, owned by
the Company either directly or through one or more Subsidiaries.

     "Thayer Holdings" means Thayer ITECH Holdings, L.L.C.


                                 ARTICLE VIII
                                 MISCELLANEOUS
                                 -------------

     8.1 Expenses. The Company agrees to pay, and hold Thayer Holdings harmless
         --------
against liability for the payment of, (i) the fees and expenses of Thayer
Holdings' counsel arising in connection with the negotiation and execution of
this Agreement and the consummation of the transactions contemplated by this
Agreement, (ii) the fees and expenses incurred with respect to any amendments or
waivers (whether or not the same become effective) under or in respect of this
Agreement and the Certificate of Incorporation, (iii) stamp and other taxes
which may be payable in respect of the execution and delivery of this Agreement
or the issuance, delivery or acquisition of any shares of Stock purchased
hereunder or in accordance with Section 1.3 hereof, and (iv) the fees and
expenses incurred with respect to the interpretation or enforcement of the
rights of Thayer Holdings granted under this Agreement and the other agreements
contemplated hereby and the Certificate of Incorporation and the Company's
bylaws.

     8.2 Remedies. Each holder of Investor Stock shall have all rights and
         --------
remedies set forth in this Agreement and the Certificate of Incorporation and
all rights and remedies which such holders have been granted at any time under
any other agreement or contract and all of the rights which such holders have
under any law. Any Person having any rights under any provision of this
Agreement shall be entitled to enforce such rights specifically (without posting
a bond or other security), to recover damages by reason of any breach of any
provision of this Agreement and to exercise all other rights granted by law.

     8.3 Consent to Amendments. Except as otherwise expressly provided herein,
         ---------------------
the provisions of this Agreement may be amended and the Company may take any
action herein prohibited, or omit to perform any act herein required to be
performed by it, only if the Company has obtained the written consent of the
holders of a majority of the outstanding shares of Investor Common. No other
course of dealing between the Company and the holder of any Stock or any delay
in exercising any rights hereunder or under the Certificate of Incorporation

                                      -8-
<PAGE>

shall operate as a waiver of any rights of any such holders. For purposes of
this Agreement, shares of Stock held by the Company or any Subsidiaries shall
not be deemed to be outstanding.

     8.4 Survival of Representation and Warranties. All representations and
         -----------------------------------------
warranties contained herein or made in writing by any party in connection
herewith shall survive the execution and delivery of this Agreement and the
consummation of the transactions contemplated hereby, regardless of any
investigation made by any Purchasers or on their behalf

     8.5 Successors and Assigns. Except as otherwise expressly provided herein,
         ----------------------
all covenants and agreements contained in this Agreement by or on behalf of any
of the parties hereto shall bind and inure to the benefit of the respective
successors and permitted assigns of the parties hereto whether so expressed or
not. In addition, and whether or not any express assignment has been made, the
provisions of this Agreement which are for the Purchaser's benefit as a
purchaser or holder of Stock are also for the benefit of, and enforceable by,
any permitted subsequent holder of such Stock. The rights and obligations of the
Thayer Holdings under this Agreement and the agreements contemplated hereby may
be assigned by the Thayer Holdings at any time, in whole or in part, to any
investment fund managed by TC Management Partners, L.L.C. or any other Affiliate
of Thayer Holdings, or any successor thereto.

     8.6 Severability. Whenever possible, each provision of this Agreement shall
         ------------
be interpreted in such manner as to be effective and valid under applicable law,
but if any provision of this Agreement is held to be prohibited by or invalid
under applicable law, such provision shall be ineffective only to the extent of
such prohibition or invalidity, without invalidating, the remainder of this
Agreement.

     8.7 Counterparts. This Agreement may be executed simultaneously in two or
         ------------
more counterparts, any one of which need not contain the signatures of more than
one party, but all such counterparts taken together shall constitute one and the
same Agreement.

     8.8 Descriptive Headings; Interpretation. The descriptive headings of this
         ------------------------------------
Agreement are inserted for convenience only and do not constitute a Section of
this Agreement. The use of the word "including" in this Agreement shall be by
way of example rather than by limitation.

     8.9 Governing Law. This Agreement and the exhibits and schedules hereto
         -------------
shall be governed by and construed in accordance with the internal laws of the
State of Delaware, without giving effect to any choice of law or conflict of law
provision or rule (whether of the State of Delaware or any other jurisdiction)
that would cause the application of the laws of any jurisdiction other than the
State of Delaware.

                                      -9-
<PAGE>

     8.10 Notices. All notices, demands or other communications to be given or
          -------
delivered under or by reason of the provisions of this Agreement shall be in
writing and shall be deemed to have been given when delivered personally to the
recipient by reputable express service (charges prepaid), 24 hours after being
sent by overnight courier service (charges prepaid), 48 hours after being
deposited to the recipient by United States mail, first class, postage prepaid,
or sent by facsimile. Such notices, demands and other communications shall be
sent to the Purchasers and to the Company at the address indicated below:

                  If to the Company:
                  -----------------

                    Iconixx Corporation
                    8300 Boone Boulevard
                    Suite 250
                    Vienna, Virginia 22182
                    Attention:    Jason Levine
                                  Graham Perkins
                    Tel No:  (703) 790-9276
                    Fax No:  (703) 790-9033


                  If to the Purchasers:
                  --------------------

                    To each Purchaser at the address set forth in the Schedule
                                                                      --------
                    of Purchasers attached hereto
                    -------------

                  with a copy to:

                    Hogan & Hartson, LLP
                    Thirteenth Street, N.W.
                    Washington, D.C.  20004
                    Attention:    Christopher J. Hagan
                    Tel No.: (202) 637-5600
                    Fax No.: (202) 637-5910

or to such other address or to the attention of such other person as the
recipient party has specified by prior written notice to the sending party.

     8.11 Entire Agreement. Except as otherwise expressly set forth herein, this
          ----------------
document embodies the complete agreement and understanding among the parties
hereto with respect to the subject matter hereof and supersedes and preempts any
prior understandings, agreements or representations by or among the parties,
written or oral, which may have related to the subject matter hereof in any way.

                      [THIS SPACE INTENTIONALLY LEFT BLANK]

                                     -10-
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement on the
date first written above.


                                       ICONIXX CORPORATION


                                       By:      /s/ Graham Perkins
                                              ----------------------------------
                                              Name: Graham Perkins
                                              Title: Vice President/CFO


                                       THAYER ITECH HOLDINGS, L.L.C.

                                       By:    Thayer Equity Investors, IV, L.P.
                                       Its:   Managing Member
                                       By:    TC Equity Partners, L.L.C.
                                       Its:   General Partner


                                       By:      /s/ Robert Michalik
                                              ----------------------------------
                                              Name:     Robert Michalik
                                              Title:    Vice President


                                       TC ITECH, L.L.C.


                                       By:      /s/ Robert Michalik
                                              ----------------------------------
                                              Name: Robert Michalik
                                              Title:   President


                                       [OTHER PURCHASERS]

                                     -11-
<PAGE>

                             SCHEDULE OF PURCHASERS


<TABLE>
<CAPTION>
                                                                         Number of Shares
                                                 Number of Shares           of Class A               Aggregate
                                                   of Common at            Preferred at           Investment ($)
       Name and Address of Purchaser                  Closing                 Closing               at Closing
--------------------------------------------    --------------------    --------------------    --------------------
<S>                                             <C>                     <C>                     <C>
Thayer Equity Investors IV, L.P.                3,000,000                     16,100                 20,000,000
c/o Thayer Capital Partners
1455 Pennsylvania Avenue, NW, Suite 350
Washington, D.C. 20004
Attention:        Robert Michalik

Tel No:           (202) 371-0150
Fax No:           (202) 371-0391









                                                --------------------    --------------------    --------------------
                  TOTAL                         3,000,000                     16,100                $20,000,000
                                                ====================    ====================    ====================
</TABLE>

                                     -12-
<PAGE>

                               JOINDER AGREEMENT
                         TO EQUITY PURCHASE AGREEMENT
                         ----------------------------



     This Joinder Agreement (this "Joinder") is made as of the date written
below by the undersigned (the "Joining Party") and certain parties to the Equity
Purchase Agreement, dated as of March 22, 2000 (the "Equity Purchase
Agreement"), by and among Iconixx Corporation, a Delaware corporation (the
"Company"), Thayer ITECH Holdings, L.L.C., a Delaware limited liability company
("Thayer Holdings") and TC ITECH, L.L.C. a Delaware limited liability company
("TC ITECH"). Capitalized terms used but not defined herein shall have the
meanings given such terms in the Equity Purchase Agreement.

     Pursuant to the Equity Purchase Agreement, the Company has sold to Thayer
Holdings an aggregate of 3,000,000 shares of Common Stock, par value $0.01 per
share, of the Company ("Common Stock") at a price of $1.30 per share and an
aggregate of 16,100 shares of Convertible Class A Preferred Stock, par value
$0.01 per share, of the Company ("Preferred Stock") at a price of $1,000 per
share. The Joining Party, as a stockholder of the Company, is entitled to
purchase from the Company up to 86,250 shares of Common Stock and up to 462.875
shares of Preferred Stock.

     By executing this Joinder, the Joining Party agrees to purchase from the
Company 86,250 shares of Common Stock at a price of $1.30 per share and 462.875
shares of Preferred Stock at a price of $1,000 per share, for an aggregate
purchase price of $575,000, according to the terms and subject to the conditions
set forth in the Equity Purchase Agreement.

     Accordingly, the Joining Party hereby acknowledges, agrees and confirms
that, by its execution of this Joinder, the Joining Party will be deemed to be a
party to the Equity Purchase and shall have all of the rights and obligations of
a "Purchaser" thereunder as if he or she had executed the Equity Purchase
Agreement. The Joining Party hereby ratifies, as of the date hereof, and agrees
to be bound by, all of the terms, provisions and conditions contained in the
Equity Purchase Agreement.








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     IN WITNESS WHEREOF, the undersigned has executed this Joinder Agreement as
of the date written below.


Date:  April 17, 2000




                                 THE JOINING PARTY:
                                 -----------------


                                 FBR TECHNOLOGY VENTURE PARTNERS, L.L.C.


                                 By:     /s/ Gene Riechers
                                         ---------------------------------------
                                 Name:   Gene Riechers
                                 Title:  Managing Director



                                 APPROVED BY:
                                 -----------


                                 ICONIXX CORPORATION


                                 By:     /s/ Jason H. Levine
                                         ---------------------------------------
                                 Name:   Jason H. Levine
                                 Title:  General Counsel



                                 THAYER ITECH HOLDINGS, L.L.C.


                                 By:     Thayer Equity Investors IV, L.P.
                                 Its:    Managing Member

                                         By:     TC Equity Partners IV, L.L.C.
                                         Its:    General Partner

                                                 By:     /s/ Robert E. Michalik
                                                         -----------------------
                                                 Name:   Robert E. Michalik
                                                 Title:  Vice President